
amSBBUJ— 

Copyright]^? 

CilSXRIGHT DSPOSm 



An Essay 

on the 

Physiology of Mind 

An Interpretation Based on Biological^ 
Morphological^ Physical and 
Chemical Considerations 



BY 

Francis X. Dercum 

A.M., M.D., Ph.D. 

Member of the American Philosophical jSociety; Fellow of the 

College of Physicians of Philadelphia; Member of the Academy 

of Natural Sciences of Philadelphia; Professor of Nervous and 

Mental Diseases in the Jefferson Medical College, etc. 



Philadelphia and London 

W. B. Saunders Company 

1922 




Copyright, 1922, by W. B. Saunders Company 



MADE IN U. S. A. 



PRESS OF 

W. B. SAUNDERS COMPAN" 

PHILADELPHIA 



FEB 131922 
a>r.!&654730 



& I 



Tliis Essay is Reverentially 

Inscribed to the Memory 

of 

JOSEPH LEroY 

to whom especially we owe our 

Knowledge of the Behavior 

of the 

Rhizopoda 







Copyright, 1922, by W. B. Saunders Company 



MADE IN U. S. A. 



PRESS OF 

W. B. SAUNDERS COMPANY 

P H I U A D E l_ P H I A 



FEB 13 1922 



Oa^ I 



This Essay is Reverentially 

Inscribed to the Memory 

of 

JOSEPH LEIDY 

to whom especially we owe our 

Knowledge of the Behavior 

of the 

Rhizopoda 



Digitized by the Internet Archive 
in 2011 with funding from 
The Library of Congress 



http://www.archive.org/details/essayonphysiolpgOOderc 



FOREWORD 



In this essay the writer has endeavored to 
present the basic facts of those reactions of the 
organism to the environment which under 
given conditions manifest the quahties which 
we speak of as ''mind/' As far as possible 
elemental truths have been sought in a con- 
sideration of the structure of the constituent 
substance of the organism, the living proto- 
plasm. The physical peculiarities of the latter, 
its ceaseless chemical change, its simultaneous 
up-building and reduction, its . reactions and 
its lack of reactions to the incident forces of the 
physical world, have, in turn, been called to the 
attention of the reader. Secondly, the behavior 
of simple unicellular forms of life has been 
compared with and in a measure correlated with 
the behavior of the individual cells of multi- 
cellular forms. 

In due course, also, have been considered 
those peculiarities of structure of the living 
protoplasm which cause the arrest of certain, 
a very limited number, of the incident forces 
of the environment; protoplasm as a whole is 
''transparent'' to and remains totally unaffected 
by an infinitude of forces active in the universe. 

3 



4 FOREWORD 

In turn the writer has taken up the problems 
of the reception and transmission of the forms 
of energy which protoplasm is capable of re- 
ceiving, the conversion of these incident forces 
into other forms, and the transmission and the 
release of energy by the protoplasm itself. 
Naturally, this discussion is preceded by a 
consideration of elementary responses to im- 
pacts, by a consideration of the differentiation 
in metazoa of special structures for the recep- 
tion and transmission of the latter, and for the 
resulting expression in motion; and, finally, by a 
consideration of the elaboration and differentia- 
tion of these phenomena in the more complex 
metazoa. 

At first the responses of the organism are 
very general in character. Soon, however, 
they become limited and special, and later 
acquire the character of being fixed, stereotyped, 
and invariable. Later still, owing to an increase 
• — an increase which finally becomes vast^ — 
in the number of the integers concerned in 
transmission and owing to the preservation in 
these integers of certain primitive and undiffer- 
entiated properties, the responses lose this 
quality of fixation. They become capable of 
variation and acquire the quality of being more 
and more adaptable and adjustable to the 
impacts received; the responses become more 



FOREWORD 5 

and more the exact or, rather, the increasingly 
approximate equivalents of the impacts. 

The recondite problems of consciousness now 
present themselves and its elemental phenomena 
first occupy our attention. Finally, the writer 
directs attention to some of the remarkable 
physical facts definitely known in regard to the 
responses of the organism, facts which possess 
a profound significance and which must pro- 
foundly influence our conceptions both of the 
structure of protoplasm and of the limitations 
which this structure imposes. Here appears 
the great question: ''What and how much 
does our structure permit us to know.?'' 

In conclusion the writer wishes to say for the 
lay reader into whose hands this essay may fall, 
that as far as practicable the language employed 
has been as simple as the nature of the subject 
permits. Unfortunately, however, many tech- 
nicalities are unavoidable, though, whenever 
possible, the meaning of these has been indicated 

in the text. 

F. X. D. 

1719 Walnut Street, 

Philadelphia, Pa. 

January^ 1922, 



CONTENTS 



PAGE 

Attitude Toward the Subject 11 

Reactions of Unicellular Forms and of the Individual 

Cells of Multicellular Forms 12 

Primitive Responses of Movement in Multicellular 

Forms . 15 

Differentiation of a Contractile Cell 16 

Transmission of Impacts 19 

Primitive Pathways of Transmission 21 

Differentiation of a Receiving Cell 23 

Differentiation of an Intermediate Cell 24 

Position of the Primitive Transmitting Apparatus. 
Position Later Assumed in the More Complex 

Metazoa 24 

Structure of the Primitive Transmitting (Nervous) 

Network 26 

Differentiation of a Synaptic Nervous System 27 

The Neurone 28 

Polarity of Transmission 30 

Mechanism of Response 31 

Differentiation of Responses 33 

Impacts Which Living Protoplasm is Capable of 

Receiving 34 

Chemical Impacts 34 

Impacts from Movements and Coarse Vibrations in 

the Surrounding Medium 35 

The Otic Vesicle, the Ear, the Lateral Line 35 

Impacts of Light, of Heat 37 

Limited Capacity of Living Protoplasm for the 
Reception of the Incident Forces of the Environ- 
ment. Significance of this Fact 39 

Differentiation of the Receptors. Physical Character 

of their Function 42 

7 



8 CONTENTS 



PAGE 



Methods of Response by the Organism 47 

EstabHshment of Definite Pathways of Transmission. 

The "Common Paths" 48 

Segmental Relations of the Central Nervous Appa- 
ratus 49 

Segmental Relations of the Cephalic Extremity and 

the Special Sense Receptors 50 

The Nose Brain, Eye Brain, Ear Brain, Skin Brain, 

Visceral Brain 50 

The Chemical Sense. Automatism of Response in 
the Approach to or Withdrawal from Foreign 

Bodies 51 

Roles of the Other Senses 54 

Automatic Character of the Spinal Responses 55 

The Palseo-encephalon; the Brain Stem; Responses 

Fixed, Invariable 56 

The Neo- or Telencephalon; the Cortex; Responses 

Variable and Adaptable 57 

Absence of Segmental Relations of the Telencephalon 57 
Pathways of Ingress and Egress to the Telencephalon 58 
Functions of the Cortex; the So-called Centers. As- 
sociation Pathways. Relation of the Various Parts 
of the Cortex to Each Other. Possibilities of 

Adaptation and Adjustment of Responses 60 

The Responses of the Cortex Being Variable the 
Neurones Cannot Be in Fixed Relations with Each 

Other 62 

Amoeboidism of Cortical Neurones; Historical Data. 

Discussion 63 

The Neuroblast. Chemo taxis; Neurobiotaxis 67 

The Synapses. Polarization of the Neurone 70 

Further Discussion of the Amoeboidism of the Neurone 71 

Synaptic Delay 72 

The Electro-endosmotic Layer 74 

Amoeboid Transmission. The Neurone Threshold. . . 78 



CONTENTS 9 



PAGE 



The Principles that Determine Neurobiotaxis and th^ 
Principles that Determine the Direction of Trans- 
mission. Old and New Pathways of Transmission 79 

Changes in the Neurone. Release of Energy. Ava- 
lanche Conduction 81 

Consciousness. Sentiency. The Lower Forms of 
Life; the Lower Vertebrates; the Higher Verte- 
brates. The Role of the Pallium; the R61e of the 
Palseo-encephalon . 83 

In Mammals Fixed Responses Play no Role in 
Consciousness 86 

Disappearance of Consciousness in Acquired Autom- 
atisms 87 

Consciousness Present Only in Responses of Adapta- 
tion and Adjustment 88 

Phenomena of Transmission Through the Cortex. 
Relations of These Phenomena to Consciousness.. . 89 

Nature of Consciousness . 90 

Principles that Govern Transmission 93 

The Train of Activity. The Field of Consciousness. 
Community of Consciousness, Sense of SeK 95 

Memory; its Automatism. Instincts . 96 

Perception; Apperception; Thought 99 

The Conscious and the Unconscious Fields. Physi- 
ology of the Latter 101 

The Re-forming of Old and the Formation of New 
Combinations Among the Neurones; Originality; 
Imagination 103 

Relative Dynamic Power of the Conscious and Un- 
conscious Fields. Dynamic Levels. Attention; 
Concentration; Initiative; Will Power 105 

Sentiency. Sensation. Role of the Telencephalon. . 106 

Special Sensations Derived from Physical Impacts. - 
Extero-, Intero-, and Proprioceptors. Pleasure, 
Pain, The Emotions; Affects. 107 



10 CONTENTS 



PAGE 



Physical Conceptions in the Interpretation of Mind 114 

Significance of the Element of Time 115 

Significance of Weber's Law 116 

Inferences as to the Changes in the Striictm^e of 
Protoplasm in Response to Changes in the Outside 

World 118 

Limitations of Possibilities : 

a, Only Such Changes as Protoplasm is Capable of 

Receiving; 
by These Changes Correspond Only Imperfectly 

to Changes in the Outside World 119 

Memory Pictures; Composite Pictures; Abstract 

Conceptions; Abstract Thinking; Dangers 120 

Final Word as to the Biological Interpretation of Mind : 
Objections to the Greek Word (po;(7j and Its 

Derivatives. 
Objections to the Latin Word Spiritus and Its 
Derivatives 122 



ADDENDUM 

The Pathological Physiology of Mind , 126 

Hysteria, Hypnosis, Dreams 127 

Delirium, Confusion, Stupor 131 

Hallucinations, Illusions, Delusions 132 

Variability of Neurone Relations 133 

The Biological Endogenous Deteriorations. The 

Precocious Dementias. The Paranoid States 134 

The Appearance and Significance of Fixation 138 

Melancholia, Mania 139 

Index 143 



AN ESSAY 

ON THE 

PHYSIOLOGY OF MIND 

An Interpretation Based on Biological, 
Morphological, Physical, and Chemical 
Considerations 



To the writer it has seemed that all of the 
phenomena embraced by human experience, no 
matter what their character, must be approached 
from the standpoint of cold, unemotional, sci- 
entific observation and analysis. This neces- 
sitates as a preliminary an attitude of mind in 
which preconceived ideas, prejudices of what- 
soever character, previous beliefs, and concep- 
tions are set aside. In no field is this more 
important that in the study of the phenomena 
embraced under the term ''mind.'' Long the 
subject of the discussions of metaphysicians and 
in later times of psychologists, the phenomena 
of mind have been approached as though they 
were altogether peculiar in their character and 



11 



12 THE PHYSIOLOGY OF MIND 

being; as though a difference essential and in- 
trinsic separated these phenomena by a wide 
and hopeless gap from all other phenomena of 
nature. Let us see whether such an attitude, 
such a preconceived notion, is justified. 

When we turn our attention to some of the 
lower forms of life, for example, to the pro- 
tozoa, and notably to the simple expression of 
life as witnessed in the amoeba, we find that the 
organism reacts in an already complex manner 
to the environment; thus, when the pseudopod 
of an amoeba comes in contact with a foreign 
body one of two things occurs: either the pro- 
toplasm of the pseudopod flows around the for- 
eign body and thus takes the latter into the 
interior of its own substance, or the pseudopod 
is withdrawn. Here we have undoubtedly a 
''selective'' action. If the foreign substance is 
capable of serving as food, it is appropriated; if 
not, it is rejected. Should the foreign body be 
made up both of material capable of serving as 
food and of material incapable of serving such 
a purpose, the two are separated; after a time 
the first disappears, apparently becomes a part 
of the substance of the amoeba; the second is 
ejected. No one, I believe, would be so ven- 



THE PHYSIOLOGY OF MIND 13 

turesome as to interpret these phenomena as 
the voHtional acts which they so closely re- 
semble. Evidently they are merely the result 
of the physical (or physico-chemical) reaction 
of the protoplasm of the amoeba with the ma- 
terial of the foreign body. Our increasing knowl- 
edge of the functions of the cells in the higher 
animals has taught us that not only have these 
cells the special functions pertaining to the tis- 
sues of which they are parts but also that they 
retain, in addition, the primordial property of 
selecting, digesting, and assimilating their own 
food. It would appear that the cells of the 
various tissues possess each a special structure, 
a special metabolism; that is, each cell contains 
special ferments by means of which it builds 
itself up, adds to its own substance out of the 
general material of the blood plasma. The cells 
thus have the power of ^ ^selecting'' foreign 
materials, of fragmenting them, and of utilizing 
them for purposes of reconstruction or as sources 
of energy. The purely physical character of 
these changes are, of course, beyond question. 
Fats are split into alcohol and fatty acids; car- 
bohydrates are broken up; albumin is con- 
verted into peptones; the latter are split into 



14 THE PHYSIOLOGY OF MIND 

amino-acids and these again into still simpler 
bodies. In turn, the cells give up into the 
blood-stream substances so far reduced that 
they are no longer sources of energy, can no 
longer play a role in the metabolism of the cell. 
Not only have the cells of multicellular forms 
retained the power of selecting, appropriating, 
and discarding the various materials concerned 
in their metabolism, but such cells as are not 
fixed in the tissues, e. g., the white corpuscles 
of the blood, have retained in addition the 
power of independent movements and of act- 
ually extending and retracting portions of their 
substance in every way comparable to the 
pseudopods of the amoeba. Surely no one 
would ascribe the action of the individual cells 
of the multicellular animals to volition. Both 
the ''selective'' action and the power of reduc- 
ing the material selected into components suit- 
able for appropriation into its own substance 
are properties inherent in living protoplasm and 
which the tissue cell shares with the most prim- 
itive unicellular forms. No volitional, no so- 
called ''psychic" act can be considered as enter- 
ing into the phenomena. It seems almost super- 
fluous to repeat that they are clearly the result 



THE PHYSIOLOGY OF MIND 15 

of purely physical and chemical processes. They 
merely instance the action of colloidal sub- 
stances upon each other and upon other sub- 
stances; an action in which the ions of the con- 
tained crystalloids no doubt also play a part; in 
short, the problem is one of chemistry, of elec- 
tromagnetic or equivalent reactions. 

We have in the selection and appropriation of 
food by the cells of the tissues an instance of 
the retention by the individual cells of multi- 
cellular organisms of the primitive properties of 
the single cell of unicellular forms. When we 
turn our attention in multicellular forms to 
other properties which have likewise to do with 
the reaction of the organism to the environment, 
other equally interesting facts become apparent. 
Let us begin with sponges. According to 
Parker,^ ''Some sponges, such as the Stylatella, 
appear, when out of w^ater, to be more or less 
shrivelled or contracted and under other cir- 
cumstances to be plump and w^ell rounded out. 
The differences which, for reasons to be men- 
tioned presently, are known not to be due to 
the simple physical loss of fluid, are apparently 

^ G.. H. Parker, Sc.D., "The Elementary Nervous System," Phila- 
delphia and London, J. B. Lippincott Company, p. 26. 



16 THE PHYSIOLOGY OE MIND 

dependent upon a general contractility of the 
whole flesh of the sponge which, though slight, 
may nevertheless enable the sponge to change 
its form somewhat." Again, the dermal mem- 
brane of sponges which is a tissue which has not 
become differentiated into cells, but remains 
syncytic, has the property of closing the pores 
of the sponge apparently by flowing over and 
coalescing, thus forming ''over the external end 
of the pore canal an extremely thin sheet, the 
pore membrane, near the middle of which the 
pore has disappeared."^ The movement of the 
pore membrane ''is hardly to be described as 
purely amoeboid. It seems to represent a stage 
of differentiation between amoeboid motion and 
simple muscle contraction which may well in- 
dicate the kind of contractility that the com- 
mon flesh of the sponge possesses. "^ In addi- 
tion, the pores may be closed in some sponges 
not only by the formation of a pore membrane 
but also by the closure of the canal leading to 
the pore — the pore canal — itself. "This is prob- 
ably due, according to Wilson, to a contraction 
of the epithelial lining in the pore canal acting 
after the fashion of a sphincter."^ The cells of 

1 See Parker, loc. cit., p. 34. ^ Lqc. eit., p. 36. ^ Loc. cit., p. 35. 



THE PHYSIOLOGY OF MIND 17 

this epithelial lining '^are in every way com- 
parable to a primitive form of smooth muscle- 
fiber. Their superficial position places them in 
contact with the water passing through the canal 
and, as they respond to differences in this 
water, they are without doubt capable of direct 
stimulation." To repeat, then, we have in the 
sponges not only a general contractility of the 
organism as a whole, together with an amoeboid 
movement of the dermal membrane, but also a 
sphincter-like action in the canals due to spe- 
cialized cells. The latter correspond to the 
smooth muscle cells of other metazoa. They 
have, of course, no nerve supply and are de- 
pendent for their stimulation to contraction on 
the physical contact with the changing water 
and its contained substances. 

It is interesting to note that in the higher 
animals muscle-fibers still exist which like these 
primitive muscle cells of sponges are capable of 
responding to direct physical stimulation inde- 
pendently of any nervous influence. This has 
been clearly demonstrated, for instance, by a 
number of observers to be the case in the irij. 
In fishes, amphibians, birds and mammals, and 
probably in the eyes of cephalopods, the sphinc- 



18 THE PHYSIOLOGY OF MIND 

ter of the pupil may be regarded as normally 
subject to direct stimulation by light, notwith- 
standing the fact that it is also under nervous 
control.^ Similarly, the vertebrate heart mus- 
cle appears to be equally subject to direct phys- 
ical stimulation. While the adult heart is 
abundantly supplied with nerves and, indeed, 
itself contains an abundance of nerve-cells, no 
such facts obtain, so far as is known, in regard 
to the developing heart of the embryo. Indeed, 
in the chick the heart appears in about twenty- 
three hours of incubation and begins to pulsate 
about six hours later, at a time when the neural 
crests and neuroblasts have not yet been dif- 
ferentiated. Hence, there is every reason to 
believe that in the beginning it is absolutely 
free from possible nervous influence and that its 
beat is purely myogenic. ^ Many similar in- 
stances of muscle activity independent of ner- 
vous influence might be cited. It is true ap- 
parently of the heart of the tunicate, of the 
muscle-fibers of the amnion of the chick, and of 
the circular and acontial fibers of sea-anemones.^ 
We have, then, as one of the primary facts of 

^ See Parker, loc. cit., pp. 50-53. ^ j^qq (>it., pp. 53-56. 

^ Loc. cit., pp. 59-61. 



THE PHYSIOLOGY OF MIND 19 

the reaction of the organism to the environ- 
ment a response in movement. This is expressed 
in the amoeba in the movements of its pseudo- 
pods, and, in such multicelhilar forms as the 
sponges, in the movements of the syncytic 
dermal membrane, in the contraction of the 
cells about the canals, and in the movement of 
the bodv of the animal as a whole. 

The next question that presents itself is as to 
the capacity of living protoplasm for the trans- 
mission of motion through its own substance. 
It is not my intention to take up at this point 
the reaction of protoplasm to light, to heat, to 
electricity, or to sound, but rather its reaction 
to those more grossly mechanical forces implied 
by the impact of foreign bodies. In the sense 
here employed mere contact implies such an 
impact. To begin, if transmission of a mechan- 
ical impact actually takes place, it would not be 
surprising to find that this transmission is rela- 
tively slow. Proteins are extremely complex 
compounds. They are made up of many 
amino-acids; as many as seventeen. Emil 
Fischer, it may be recalled, succeeded in com- 
bining as many as nineteen amino-acids in the 
synthetic construction of an artificial protein* 



20 THE PHYSIOLOGY OF MIND 

It is a legitimate inference from these and other 
facts that the structure of Kving protoplasm is 
that of an exceedingly complex colloid, the dis- 
perse and continuous phases of which must 
necessarily bear multiple and complicated rela- 
tions of surface and interfacial tension and of 
electrical charge to each other. It would seem 
that considerable time relatively must neces- 
sarily elapse for the diffusion or transmission of 
a mechanical impact through such a substance. 
That transmission or diffusion takes place 
from one part of a protozoan to another part as 
a result of impact or contact is exceedingly 
probable. In the amoeba the transmission ap- 
pears to be more or less widely diffused, for not 
only a pseudopod but the organism as a whole 
may move toward the food. The diffusion, 
however, appears to be very slow. In simple 
multicellular forms such as the sponges trans- 
mission likewise takes place. Thus, Parker 
states^ that if a pin is stuck into a finger of 
Stylatella at 1^ cm. from the osculum, the 
osculum will close in about ten minutes; and 
further, that ""the sluggish transmission upon 
which this reaction depends represents without 

1 See Parker, loc. cit., p. 42. 



THE PHYSIOLOGY OF MIND 21 

doubt that elemental property of protoplasmic 
transmission from which true nervous activity 
has been evolved. It may, therefore, not in- 
appropriately be called neuroid transmission. "^ 
Similarly, in other animals a transmission of 
motion through non-active and non-nervous 
protoplasmic tissue can be demonstrated as 
when motion is transmitted from one field of 
cilia to another, although quiescent or non- 
ciliated tissues lie between. According to 
Parker, ^'it appears that the ordinary tissues of 
animals, at least their ciliated epithelia, may 
exhibit sluggish forms of transmission that are 
so like those seen in sponges as to admit of being 
classed under the single head of neuroid trans- 
mission."^ 

Obviously, it is greatly to the advantage of 
an organism when special pathways for trans- 
mission are differentiated. Such pathways make 
their appearance in the primitive nervous appa- 
ratus of coelenterates. This nervous apparatus 
has been elaborately studied in jelly-fishes and 
sea-anemones. In the former, impressions — 
stimuli — upon the marginal bodies are diffused 
through deeper lying muscle-cells, so that a 

1 See Parker, loc. cit., p. 64. ^ Loc. cit., p. 75. 



22 THE PHYSIOLOGY OF MIND 

contraction takes place in the large circular 
sheet of muscle that forms the sphincter-like 
organ midway between the centrally located 
mouth and the edge of the bell. This contrac- 
tion reduces the cavity of the bell and by thus 
driving the water out of this cavity forces the 
animal forward.^ 

In the sea-anemones an impulse — -a mechan- 
ical stimulus — applied to the surface of the ani- 
mal results in a retraction of the oral disc. 
Investigations have shown that the impulse 
both in the jelly-fish and the sea-anemone is 
diffused through a well-defined nervous net- 
work. When this nerve tissue is studied it is 
found to consist of a diffuse and continuous 
network which also contains cells. The fact 
that the network is continuous and diffuse sug- 
gests an analogy to the syncytic tissue of the 
dermal layer of the sponges. In keeping, how- 
ever, with what one would expect, the evolu- 
tion of special pathways for transmission, leads 
— judging by the time of the response — to an 
increased speed of transmission; the response, 
which is very slow in sponges, is much more 
rapid in the coelenterates. 

^ See Parker, loc. cit., p. 103. 



THE PHYSIOLOGY OF MIND 2S 

Let us now turn our attention once more to 
the primitive muscle-cell in the pore canals of 
the sponges. This muscle, as we have seen, sug- 
gests the smooth, unstriated muscle-cell of the 
higher animals; indeed, such a muscle-cell is 
still found in some of the tissues of the latter 
existing as a prototype independent of nervous 
influence. A muscle-cell independent of ner- 
vous influence reacts directly, as we have seen, 
to a stimulus applied to it. This is unques- 
tionably the case in the muscle-cell in the pore 
canal of the sponge, in which the stimulus is 
the flowing water and the substances contained 
in the latter; similar facts obtain in the case of 
the other independent smooth muscle-cells that 
have been instanced. In the sea-anemones and 
the jelly-fishes, however, the muscle-cell no 
longer receives its stimulus directly from the 
environment. There is now interposed an epi- 
thelial cell which receives the stimulus and 
transmits it to the muscle-cell. This epithelial 
receiving cell acts as a ''sense" cell and is 
termed the ''receptor," while the muscle-cell to 
which it conveys the stimulus is known as the 
''effector." Later a third structure appears inter- 
posed between the receiving cell and the muscle- 



24 THE PHYSIOLOGY OF MIND 

cell. The function of the new structure, a cell 
termed by Parker "protoneurone/' appears to 
be to diffuse and to distribute to the muscle- 
cell or cells the stimulus derived from the re- 
ceiving cell. Its function is that of an inter- 
mediary. Evidently we have presented here an 
arrangement which is the prototype of the 
sensory, nervous, and muscular system of the 
higher animals. 

Certain other important considerations now 
present themselves. In the higher animals the 
nervous system, which in sea-anemones and 
jelly-fishes is largely superficial, existing in the 
epithelial layers of the animal, becomes grad- 
ually more and more deeply seated and better 
protected. This is seen in the higher inver- 
tebrates and vertebrates alike. In invertebrates 
there is a gradual retreat, a migration, of the 
nervous apparatus into the interior of the ani- 
mal; in vertebrates, as evidenced by embry- 
ology, a portion of the epidermal layer, a por- 
tion doubtless corresponding to a primitive area 
of receptor or sensory epithelium, becomes 
grooved and finally inclosed by the infolding of 
the edges of the groove. 

Interesting as these facts are, a still more 



THE PHYSIOLOGY OF MIND 25 

important consideration remains. The nervous 
system of coelenterates, as we have pointed out^ 
consists of a diffuse and continuous network 
which also contains cells and which is grossly 
analogous to the syncytic tissue of the dermal 
layer of sponges. Restating the facts thus far 
considered, we find that the most elemental 
form of response by an organism to the en- 
vironment — next to the movement of the pseu- 
dopod of an amoeba — consists in the contraction 
of an epithelial cell, a cell analogous to a smooth 
muscle-cell, directly in response to a stimulus. 
The next stage consists, as also pointed out, in 
the appearance of another epithelial cell which 
does not itself contract, but receives the im- 
pression or stimulus and transmits it to the 
contractile cell. In this primitive arrangement 
the first or receiving cell, the receptor, is at- 
tached directly to the muscle-cell, the eJBFector. 
As a matter of fact, a number or a group of re- 
ceiving cells are attached to a number or a 
group of muscle-cells. Further, this arrange- 
ment "is complicated by the fact that the cen- 
tral branches of the receptive cells are not only 
applied to the muscle-cells, but form among 
themselves a network of communication whereby 



^Zty THE PHYSIOLOGY OF MIND 

the impulses that arise from a few receptive 
cells may be transmitted to many muscle-cells 
instead of being limited to a restricted group/ '^ 
The final stage consists in the differentiation of 
additional cells now interposed between the 
primitive receiving cell and the muscle-cells. 
The network now becomes exceedingly com- 
plicated, but it presents this distinguishing 
feature, its fibers are continuous. The cells 
which it contains are clearly primitive nerve- 
cells and, as already stated, Parker has applied 
to them the term ^^protoneurones/' Further, 
there is no separation of these protoneurones 
from each other such as occurs in the neurones 
of vertebrates. There is a free interchange be- 
tween them of the fibers of the network. There 
is therefore a wide diffusion of transmission 
which is totally different from the transmission 
along definite paths as seen in vertebrates. It 
is interesting to note, however, in this connec- 
tion that even in vertebrates nerve nets, diffuse 
and continuous, are found in certain struc- 
tures, namely, in the walls of the intestine and 
in the heart and blood-vessels. The nerve cells 
found in these structures present all the char- 

.1 See Parker, loc. cit., pp. 200, 201. 



THE PHYSIOLOGY OF MIND 27 

acteristics of protoneurones, and as in the 
coelenterates form a continuous network. ^ 

It is, however, with the differentiated neurone 
of the central nervous system of vertebrates 
that we are most concerned. Here the cells 
which give rise to nerve-cells are in the embryo 
entirely distinct and separate, and it is only by 
developing extensions or processes that one 
nerve-cell comes into relation with other nerve- 
cells; but there is never any fusion or exchange 
of fibers between them. Each nerve-cell is a 
separate and distinct histological integer. It is 
a unit which is made up of the cell body and the 
cell processes. By means of the latter it comes 
into proximity with other nerve-cells often far 
distant. The processes terminate in brush-like 
tufts, basket-like formations, and in other ways. 
The approximated end-formations of two nerve- 
cells is spoken of very appropriately as a syn- 
apse. The nerve-cell, in general terms, is made 
up of a cell body and two kinds of processes; at 
one extremity are found one or multiple proc- 
esses leading to the cell body; these are known 
as the dendrites; at the other extremity is found 
a process leading from the cell body; this is 

1 See Parker, loc. cit., pp. 118, 128. 



28 THE PHYSIOLOGY OF MIND 

known as the axone. To this entire structure 
Waldeyer in 1891 apphed the term "'neurone/' 
which has been universally accepted and is now 
in common use. Occasionally there is more than 
one axone; quite frequently, too, the axone 
gives off small side branches, usually near the 
cell body; these are known as collaterals. 

For a discussion of nervous function clear 
conceptions of nervous structure are absolutely 
essential. To repeat, then, the neurone cor- 
responds morphologically to one cell; it is an 
anatomical and genetic unit. It comes into 
close relations with other neurones, but remains 
anatomically distinct and separate. The point 
or, rather, the structure at which the juxta- 
position of the processes of two neurones takes 
place — ^the synapse — assumes, therefore, a spe- 
cial importance in the problem of transmission.^ 
Not only the independence of the individual 
neurone but the presence of the synapse dis- 
tinguishes the nervous system of the higher 
animals from that of the coelenterates, and it 

^ Instead of the cells coming into relation by the approximation of 
the end-tufts of the axone of one cell to the dendrites of another, the 
end-tufts of the axone of one cell may terminate about the body of the 
second cell, but in neither case is there any fusion or continuity of struc- 
ture. 



THE PHYSIOLOGY OF MIND 29 

may, therefore, be spoken of as a synaptic ner- 
vous system in contrast with the nerve-net of 
the coelenterates which is essentially syncytic. 

A very important fact now becomes mani- 
fest. In the nerve net of the coelenterates trans- 
mission is essentially diffuse in character. Only 
in a very limited degree is the response to a 
stimulus differentiated. According to Parker, a 
stimulus — e. g., a fine glass rod — applied to a 
single spot on the body of a sea-anemone may 
be followed by a contraction of its whole mus- 
culature.^ However, if the stimulus be less 
vigorous and limited — e. g., if light be thrown 
on one side of the animal — it responds usually 
by turning its oral disc toward the light. Again, 
stimulation of its tentacles by food will cause its 
transverse mesenteric muscles to contract and 
thus open its oesophagus. Further, transmis- 
sion though diffuse in certain nerve-nets takes 
place more readily in one direction than in 
another; e. g.^ in the tentacles of the sea- 
anemone, in which transmission is much more 
freely accomplished in a proximal direction than 
in a distal one. This slight tendency to spe- 
cialization in the responses exhibited by the 

1 Loc. cit., pp. 99, 100, 207. 



30 THE PHYSIOLOGY OF MIND 

sea-anemone is to be looked upon as the fore- 
runner of the extremely specialized and limited 
responses met with in the higher animals. How- 
ever, while a nerve-net may transmit more 
freely in one direction than another, it really 
transmits in all. Transmission in one direc- 
tion, that is, "polarity of transmission, exists in 
a very imperfect degree in the nerve-net. In 
the synaptic nervous system, however, it is not 
only established, but is absolute. For example, 
while it is possible to elicit a response to a 
stimulus applied in the course of an afferent 
neurone of the spinal cord, as in obtaining a 
spinal reflex, no amount of stimulus applied to 
the efferent neurone, for instance, to the cen- 
tral end of a divided motor spinal root, will 
elicit any response whatever. Were it not for 
the synapses and the consequent polarity of 
the neurone, a stimulus so applied should dif- 
fuse to other neurones in the cord; e. g.^ to sen- 
sory neurones and from these again to motor 
neurones, and thus lead to a response; but none 
takes place. 

It is to the synaptic nervous system of the 
vertebrates that we will now direct our atten- 
tion. We have already seen that the smooth 



THE PHYSIOLOGY OF MIND 31 

muscle-cell of the pore-canal of the sponge re- 
sponds to a direct stimulation. In the coelen- 
terates a receiving cell is interposed between 
the muscle and the stimulus. The muscle mani- 
fests the response; it is the effector; the receiv- 
ing cell is the receptor. At the next stage of 
differentiation, as already pointed out, another 
cell is interposed which now transmits the im- 
pulse from the receptor to the effector. In ver- 
tebrates this constitutes the simplest expression 
of a response, or, to use the physiological term, 
a reflex. An impression is made on the cuta- 
neous surface, is transmitted along the dendrite 
of the afferent neurone; thence to the cell body 
of the latter; thence along its axone to its end- 
tufts which are in relation with the dendrites 
of the transmitting cell and form with the 
latter a synapse; thence to the body of the 
transmitting cell (the motor cell in the ventral 
horn of the cord), and thence by the axone of 
this transmitting cell to the end-plate on the 
muscle-fiber. The mechanism of the response 
does not, however, remain as simple as this; for 
other neurones, intercalary neurones, are fur- 
ther interposed; thus a neurone may be inter- 
posed between the afferent cell or receptor, the 



32 THE PHYSIOLOGY OF MIND 

sensory neurone, and the motor neurones. The 
ejffect of such an intercalary neurone may be 
twofold: first, it may reinforce, i. e.^ increase 
the volume and intensity of the transmission; 
secondly, it may come into relation with neu- 
rones other than the ones between which it is 
interposed and thus make possible a more ex- 
tensive and a more complicated response. An 
a priori consideration would suggest that there 
are necessarily great variations in the sim- 
plicity or complexity of the responses as well as 
wide variations in the degree with which such 
responses are fixed or stereotyped. These in- 
ferences, I need hardly add, are in accord with 
fact. In the spinal reflexes, for instance, we have 
examples of relative simplicity and stereotypy 
of response. In the knee-jerk we have an ex- 
ample of an exceedingly simple and fixed re- 
sponse. It is invariably the same and inde- 
pendent of volition; it is subject, of course, to 
variations in diffusion and degree dependent 
upon secondary factors, but its character never 
changes. The neural mechanism upon which it 
depends is relatively simple. 

However, the very simplicity and stereotypy 
of the knee reflex bespeaks a response that has 



THE PHYSIOLOGY OF MIND 33 

become differentiated and limited, and it serves 
our present purpose merely as offering an ex- 
ample of a simple mechanism of spinal re- 
sponse. It is exceedingly probable that in the 
course of development differentiations of lim- 
ited relationships between intercalary neurones 
and efferent neurones ensued relatively late, and 
that the primitive arrangement was one which 
permitted of the more or less wide diffusion of 
the stimuli received by the afferent neurones. 
In keeping with this we note in the fish in re- 
sponse to such stimuli movements which in- 
volve the musculature of the entire trunk. Evi- 
dently the mechanism of response must at first 
have been very general in character. It must 
have consisted in the linking of intercalary neu- 
rones and the consequent formation of path- 
ways of transmission general in character, and, 
furthermore, common to the transmission of 
stimuli received from many different receptors. 



Having laid a foundation for the conception 
of the mechanism by means of which stimuli are 
received and transmitted, let us now turn our 
attention briefly to the stimuli which the or- 



34 THE PHYSIOLOGY OF MIND 

ganism is capable of receiving. Thus far we 
have considered merely the most primitive of 
all stimuli, namely, contact with foreign bodies. 
Such contact constitutes an impact grossly 
mechanical or physical in character. Evidently, 
living protoplasm is, in addition, exposed to 
actions that are chemical, to the movements and 
course vibrations of the medium in which it is 
immersed, as well as to the various forces that 
pervade the physical world. 

Protoplasm is, of course, destroyed by any 
chemical action that radically interferes with 
its structure. Living protoplasm, as pointed 
out, is an exceedingly complex colloid; it is 
relatively unstable and is constantly undergoing 
change. It is being constantly built up and yet 
is being constantly oxidized and reduced. Such 
changes necessarily mean an interplay within 
comparatively narrow limits. If living proto- 
plasm is exposed, for instance, to the gross ac- 
tion of an acid or an alkali, its destruction 
necessarily follows. There is, however, a wide 
range in which chemical action can take place 
without such result. Such non-destructive ac- 
tion would naturally be influenced, first, by the 
nature of the substance diffused through the 



THE PHYSIOLOGY OF MIND 35 

surrounding medium, and secondly, by the de- 
gree of its dilution. The reaction of the proto- 
plasm to such influences cannot, of course, be 
observed by us through the microscope, but 
that such chemical actions do take place is 
evidenced to us in our own persons by our 
senses of taste and smell. Further, it will be- 
come apparent as we proceed that the reaction 
of the organism to the chemical impressions of 
the environment have profoundly influenced the 
development of the nervous system. 

When we turn our attention to the move- 
ments and vibrations of the medium in which 
the protoplasm is immersed, we at once find 
numerous evidences that the protoplasm reacts 
to such influences. In the very simplest forms, 
such as the protozoa, the coarse movements of 
the water — currents and the like — possibly facili- 
tate the changes implied by oxidation, but do 
nothing else. Soon, however, in the metazoa 
we observe the appearance of small cavities — 
vesicles — which contain one or more particles 
of solid mineral matter and which constitute an 
apparatus by means of which the movements, 
the vibrations, of the surrounding medium are 
taken up— arrested as it were- — and thus for- 



36 THE PHYSIOLOGY OF MIND 

cibly transmitted to the body of the organism. 
Such an apparatus, though it is termed an ear^ 
an otic vesicle, may take up movements far 
coarser than those which in ourselves give rise 
to sound. Again, in fishes there is, in addition 
to a well-differentiated ear, an apparatus which 
extends in linear form from the head on each 
side of the body to the tail. It is known as the 
lateral line system and consists of a tube having 
at intervals an open space closed by a mem- 
brane beneath which is found a structure in- 
distinguishable in its essential features from a 
macula acustica. Each such macula contains 
epithelial cells bearing hair-like appendages and 
each is surmounted by a small jelly-like mass 
containing a few granules of mineral matter. 
It is exceedingly probable that this apparatus, 
existing as it does in addition to the ear, has to 
do with the reception of vibrations other than 
those of sound; namely, waves and movements 
of relatively great length.^ 

It would appear, then, that in addition to the 
chemical impressions of the environment, the 
movements and vibrations of the surrounding 

^ See, among others, Dercum, Proceedings Academy of Nat. Sci., 
Philadelphia, 1879, p. 152. 



THE PHYSIOLOGY OF MIND 37 

medium are taken up in greater or less degree 
by living protoplasm. These movements seem 
to play an indifferent role in the protozoa and 
in plant life, but in metazoa an apparatus sooner 
or later makes its appearance, the function of 
which is to arrest and to transmit, and, in many 
instances, to magnify what is purely a mechan- 
ical or physical impression. 

Similarly, living protoplasm has the function 
of taking up other incident forces. Especially is 
this the case in regard to light. The simpler 
forms of life — e. g.^ the amoeba and other 
protozoa — are largely transparent to light. It 
is probable that the light vibrations so trans- 
mitted influence notwithstanding the chemical 
changes in the protoplasm; indeed, this is so 
evident in plant life as to admit of no question. 
However, very early we note in many protozoa 
the appearance of a small mass of red or dark 
red pigment, a so-called eye spot or stigma, a 
mass which clearly is not, or is less, transparent 
to light than the remaining protoplasm, and 
whose action is apparently to arrest and trans- 
form the light vibrations and, possibly, to trans- 
mit this transformed energy to the general pro- 
toplasmic mass. Clearly we have here a mech- 



38 THE PHYSIOLOGY OF MIND 

anism, a modification of structure, analogous 
to the formation of the otic vesicle, the function 
of which with its contained mineral granules 
(otoliths) is obviously to arrest and transmit 
coarse physical vibrations. 

Heat likewise greatly influences the activity 
of living protoplasm. The reactions of amoebae 
and other protozoa to variations in tempera- 
ture are well known. Whether in given forms 
the eye spots, the stigmata, play here also a 
role is not known, though it is, of course, not 
improbable. However, the presence of the 
stigmata is clearly not necessary to the tem- 
perature reactions of the primitive organism. 
All things considered, special structures for the 
^^taking up" of heat rays do not appear to be 
developed until late in the evolution of the 
metazoa, and our knowledge of them is largely 
inferential. Regarding their actual existence, 
however, there can be no doubt; of this our 
ability to appreciate hot and cold and, indeed, 
many gradations of temperature, offers indis- 
putable evidence. 

A very striking fact now becomes apparent, 
namely, that the various mechanisms for the 
special reception of the incident forces of the 



THE PHYSIOLOGY OF MIND 39 

environment are exceedingly small in number. 
They are limited to receptors for contact, for 
coarse movements and vibrations of the sur- 
rounding medium, for chemical changes, and for 
the forces of light and heat. This is essentially 
the arrangement in the higher metazoa and 
notably in our own persons. This, however, 
leaves the organism without any provision for 
the reception — appreciation — of vast ranges of 
vibrations of whose existence we have in con- 
sequence only an inferential knowledge. Be- 
sides contact, touch will give us information 
only of coarse vibrations numbering less than 
30 per second; thence, vibrations from 30 to 
30,000 per second are appreciated by the ear. 
Now ensues a great hiatus, for the organism is 
unable to appreciate any vibrations between 
30,000 per second and 3000 billion per second. 
Vibrations from 3000 billion to 800,000 billion 
are appreciated as radiant heat; 400,000 billion 
to 800,000 billion are appreciated as light. For 
vibrations from 800,000 billion to 6,000,000,000 
billion, embracing the ultra-violet rays and the 
a:-rays, there is no appreciation whatever.^ 

^ Herrick, Introduction to Neurology, second edition, p. 77. 



40 THE PHYSIOLOGY OF MIND 

When we consider the vast range and number 
of the forces at work in the universe^ the ex- 
ceedingly hmited capacity of the organism to 
become cognizant of its environment becomes 
very apparent. Living protoplasm fails utterly 
to develop receptors for these unnumbered 
manifestations of energy. Protoplasm seems to 
be ^^transparent'' to them. Have we not a 
hint here as to the structure of protoplasm.? If 
deluged by them in great volume it may be de- 
stroyed, but as ordinarily exposed in the course 
of nature to electricity, the ultra-violet ray, the 
a:-ray, and other rays it remains unaffected. It 
is very suggestive, too, that it is practically 
transparent to light rays and is obliged to de- 
velop a pigment, the stigma, the visual purple. 
Similarly, it is largely negative to coarse vibra- 
tions and requires the development of a vesicle 
with its contained otolith. 

In order that the significance of the above 
facts may be fully appreciated let us recall to 
our minds once more the nature of living proto- 
plasm. It is, as we have already pointed out, 
an exceedingly complex colloid, built up of many 
complex amino-acids distributed through varied 
disperse and continuous phases. It is a very 



THE PHYSIOLOGY OF MIND 41 

unstable compound, for it is constantly under- 
going changes. It is constantly being oxidized 
and reduced, but is as constantly being built 
up. Foreign materials, proteins, fats, and car- 
bohydrates are through its fermentative (i, e,, 
chemical, electro-physical) action fragmented 
until thev become identical in character with 
the molecules of the original protoplasmic mass 
and become part of its substance. During this 
process and in the further continuance of the 
chemical change, that is, in the continued proc- 
ess of oxidation, energy is liberated. The older 
particles are finally chemically so far reduced 
that they become inert and then spontaneously 
make their exit by solution into the surrounding 
medium. It is this continuous chemical change 
with its accompanying evolution of energy that 
constitutes the phenomenon presented by living 
matter. 1 

Evidently, if so complex and unstable a com- 
pound as living protoplasm when first evolved 
had been vulnerable to the innumerable in- 
cident forces of the universe, it could never 
have survived. Curiously, it has been almost 

^ The mineral salts — ions of the crystalloids — undoubtedly arrange 
themselves during this process in accordance with electrophysica»- 
principles, and no doubt play an important r6le. 



42 THE PHYSIOLOGY OF MIND 

wholly negative in its reaction to these. Ex- 
tremes of heat and cold, coarse physical de- 
struction, have been the most it had ordinarily 
to contend with. Excessively rarely have other 
agencies interfered with its existence. Its very 
''transparency" has been its salvation. Perhaps 
it is its complexity, its semifluidity — its very in- 
ability to take up manifold modes of motion — 
its colloidal plasticity, its peculiar molecular 
structure, that have made possible the passage 
through it of such a vast array of forces with- 
out change in its substance. After all, these 
forces do influence it and play a role in its 
physics and chemistry, but certainly that role^ 
as it occurs in nature — not in the laboratory — 
is not a destructive one. 

We have already considered (see p. 23) the 
evolution or adaptation in metazoa of a sur- 
face cell to receive external impressions, e, g.y 
of contact, and which receiving cell (receptor) 
transmits the impact or impulse to a contig- 
uous contractile cell (muscle-cell, effector) either 
directly or it may be through an intermediate 
cell or cells. Evidently these primitive surface 
cells were capable of receiving all of the im- 
pressions which the protoplasm itself was cap- 



THE PHYSIOLOGY OF MIND 43 

able of receiving. These impressions consisted 
primarily of those of contact and of coarse 
vibration. That substances contained in the 
medium in which the organism was immersed 
also affected the surface cells chemically is 
extremely probable. It seems equally clear 
that the surface cells were also affected bv 
the vibrations which give rise to sound and 
by those which give rise to heat and light. In 
both of the latter instances, however, it is evident 
that the degree and extent in which the impacts 
could be taken up depended upon the presence 
of special and probably, at first, purely incidental 
factors; on the one hand, on the presence of 
coarse mineral particles, and on the other of 
particles of pigment; ^. e,, of particles derived 
from the original protoplasm and so changed as 
to be able to arrest in a measure the incident 
forces. 

In addition, then, let us repeat, to contact 
and coarse vibrations, the primitive svirface re- 
ceiving cell also received those impacts termed 
''chemical.'" These impacts, molecular in char- 
acter, are those which, as already pointed out, 
give rise in ourselves to the sensations of smell 
and taste. It would seem that the reception of 



44 THE PHYSIOLOGY OF MIND 

chemical impressions was almost as primitive if 
not quite as primitive a quality as the reception 
of contact and coarse vibrations. On a priori 
grounds we would almost expect the chemical 
sense or senses to have assumed a relatively 
high degree of importance; and this, indeed, is 
found to be the case, judging from the facts of 
vertebrate morphology. It would appear that 
relatively early certain receiving cells became 
especially adapted to receiving chemical im- 
pressions and that this finally became their 
special and sole function. It is important at 
this point to note a distinction between the 
senses of smell and taste. The sense of smell is 
excited by objects external to the organism, 
usually by objects at some distance, and the 
impressions received from which cause the or- 
ganism to approach or to move away from the 
object. The sense of taste, on the other hand, 
deals with objects that have entered the oral 
cavity or at least come into close contact with 
it and which bring about responses within the 
body of the animal, namely, visceral responses 
dealing with digestion. As expressed by Sher- 
rington, the sense of smell is exteroceptive, while 
taste is interoceptive. Clearly, it is the extero- 



THE PHYSIOLOGY OF MIND 45 

ceptive sense of smell which deals directly with 
the environment and as such it greatly out- 
ranks in importance the sense of taste. In 
keeping with this we find in fishes that almost 
the whole of the cerebral hemisphere is an 
organ of smell, while the portion devoted to the 
sense of taste is much smaller and appears to 
be in close anatomical relation with the portion 
— the visceral area^ — devoted to impressions re- 
ceived from the viscera. However, in fishes the 
receptors for taste are found also outside of the 
oral cavity about the mouth and, indeed, in 
some forms are rather extensively distributed 
externally; so that in fishes the sense of taste is 
not as strictly interoceptive as with ourselves, 
but also in part exteroceptive. The great im- 
portance of smell as an exteroceptive sense be- 
comes evident when we reflect upon the very 
great range in the number and variety of the 
impressions, the infinitely small size of the par- 
ticles concerned, and the relatively great dis- 
tance at which they may be appreciated. 
Taste, on the other hand, has to do only with 
substances in immediate contact with the re- 
ceptors, while the variety of impressions pos- 

^ See Herrick, loc. cit., pp. 119, 273. 



46 THE PHYSIOLOGY OF MIND 

sible is exceedingly small; namely, merely salty, 
sour, bitter, and sweet. Flavors, it should be 
remembered, are appreciated only through the 
sense of smell. 

Just as in the course of development special 
receptors were differentiated for chemical im- 
pressions, special receptors were differentiated 
for the reception of sound and light, and to which 
have been adapted various structures for in- 
tensifying and elaborating the impressions re- 
ceived. A consideration of the latter factors 
would take us too far afield and, further, is not 
necessary for our purpose. Suffice it to say that 
highly specialized receptors with highly complex 
additions have in the course of time made their 
appearance, and that they are all expressive of 
a common truth, namely, that they receive and 
transmit into the interior of the organism cer- 
tain definite impacts from the external world. 
That there are more than five pathways for the 
ingress of these impacts need not here be 
pointed out; the consideration of others than 
those thus far discussed may be safely deferred 
for the present. 

Having emphasized the purely physical char- 
acter of the role played by the receptors, let us 



THE PHYSIOLOGY OF MIND 47 

turn our attention once more to the transmis- 
sion of the impacts through the organism. How 
does the organism respond to the multitude of 
impressions received? What are the reasons 
therefore? In how far are responses fixed? In 
how far are they variable? 

The simplest form of response, as we have 
already seen, is the response of a muscle-cell to 
direct stimulation; the next in the course of 
evolution is the reception by an epithelial cell, 
a receptor, of the impact, and the transmission 
of the latter to a contiguous muscle-cell, an 
effector; the third state consists in the inter- 
polation between the receptor and the effector 
of another cell whose function is that purely of 
transmitting the impact from the first cell to 
the second. This third cell may have relations, 
however, with several effectors, and thus the 
response induced may be less simple and pro- 
portionately extended. This intermediate cell 
has been termed by biologists the ^^^adjustor.'' 
It should, of course, have a definite name, but 
to the writer it has seemed that the word ''ad- 
jus tor," implying as it does independence of 
action or possibly volition, is open to objection. 
The action of the intermediate cell is purely 



48 THE PHYSIOLOGY OF MIND 

physical and, needless to say, automatic. Its 
presence, however, opens up, as we will see, 
enormous possibilities as to the degree and the 
character of the response. As already pointed 
out (see p. 31), other transmitting cells, inter- 
calary neurones, are in the course of develop- 
ment farther interposed. The role of the latter 
in increasing the volume and intensity of the 
transmission and in adding to the complexity of 
the response we have already indicated. 

Evidently the presence of the intercalary 
neurones has made possible the establishment 
of definite pathways of transmission.- Impacts 
derived from many sources would tend to form 
average pathways of transmission to the ef- 
fectors. To use the words of Sherrington, ''That 
portion of the synaptic nervous system which 
is termed 'central' is the portion where the 
nervous paths from various peripheral organs 
meet and establish paths in common, i. e.^ 
'common paths. ^ '' The central nervous system 
of vertebrates is primitively a longitudinal 
tubular structure which lies above another 
longitudinal tubular structure upon which the 
nutrition of the animal depends, namely, the 
alimentary canal. The material admitted to 



THE PHYSIOLOGY OF MIND 49 

the latter traverses its entire length. Evidently 
the reception of material which may serve as 
food is of primal importance to the animal. 
Given the '^polarity" of the latter — i. e., the 
differentiation of a cephalic and a caudal ex- 
tremity — it follows that the interplay of re- 
ceptors and effectors to bring about the intake 
of food at the cephalic end is a necessary out- 
come of the action of the individual receptors 
and the establishment of common paths of 
transmission. The primitive nervous system of 
vertebrates was in its essentials a tube in which 
the nerves coming from the peripheral surfaces 
terminated synaptically in neurones in the walls 
of the tube; probably there was an arrangement 
in segments, certain nerve aggregations corre- 
sponding to certain areas. These tubal centers 
were doubtless connected with each other by 
intercalary neurones which communicated syn- 
aptically with each other to form ^'internuncial 
paths.'' In this way many muscles would prob- 
ably be made to respond simultaneously or suc- 
cessively to an impression made upon a limited 
number of cutaneous receptors. If we turn our 
attention to the cephalic end of the animal, we 
note the presence of certain aggregations of 

4 



50 THE PHYSIOLOGY OF MIND 

neurones about the tube which stand in definite 
relation to certain receptors situated about the 
head, the relation being very much the same as 
the segmental relation in the tube lower down. 
Here, to restate the fact, definite cutaneous 
levels of receptors are related to the neurone 
aggregations at the ^ame levels, each such ar- 
rangement constituting a segment. 

The first aggregation of neurones that we 
meet with in the primitive vertebrate forms is 
that constituting the olfactory lobe which is in 
close relation with the receptors in the olfactory 
mucous membrane. Back of the olfactory lobe 
we note the presence of a lobe related to the 
receptors in the eye; next an aggregation re- 
lated to the receptors in the ear, and so on. 
Naturally these facts find their simplest ex- 
pression in the fish. Speaking of the dog-fish, 
Herrick states^ that we may recognize in this 
fish a "^^nose brain," an '^eye brain," an ^'ear 
brain," a ^Sdsceral brain," and a '^skin brain." 
Each '^brain" is related, let us repeat, to certain 
receptors and to these only. Further, each set 
of receptors and its corresponding central neu- 
rones is adapted to the reception of certain im- 

^ See Herrick, loc. cit., p. 121. 



THE PHYSIOLOGY OF MIND 51 

pacts or stimuli only; thus the receptors for the 
olfactory lobes can receive only chemical im- 
pressions; the receptors for the optic lobes only 
the impacts of light; those for the ear only the 
impacts of sound, and so on. In other words, 
each receptor can accept only its own special 
stimulus; the latter is known technically as the 
^ ^adequate" stimulus. 

We are impressed at once by the relatively 
enormous size in the fish of the olfactory lobes. 
We are justified in inferring that the chemical 
sense in fishes is most important. Its receptors 
are placed immediately above the oral cavity 
and its function in the approach of the organ- 
ism to food and in the intake of food is quite 
obvious. We note that the chemical impacts, 
^. ^., odors, are often received from great dis- 
tances. The question arises why does the 
organism as a whole respond to the reception of 
such impacts by an approach.? Here we are 
forced in a measure into the field of speculation. 
However, the phenomenon must be purely 
physical and therefore capable of a physical 
interpretation. Once more we are referred to 
the reactions of living protoplasm to the impacts 
of the external w^orld. Evidently these impacts 



52 THE PHYSIOLOGY OF MIND 

can be roughly divided into two groups: first, 
those whose motions can be taken up by the 
protoplasm with little or no consumption of its 
own substance, and, secondly, those in which 
the vibrations or molecular movements im- 
parted by the impacts tend to disrupt, to dis- 
organize, or destroy its structure. Evidently, 
chemical impressions which are in harmony or 
in consonance with the protoplasm of the ol- 
factory receptors, or, to state it in other words, 
whose chemical or physical motions are ac- 
cepted and transmitted by the receptors with 
no or a minimal change in the protoplasm of 
the latter, establish a direction of least resist- 
ance. Possibly this reaction, in its essence, 
does not differ from that which leads the amoeba 
to throw out a pseudopod toward a neighbor- 
ing mass of food. In the latter (as we have 
already seen on p. 13) we have reason to believe 
that the phenomenon is purely physical or 
dynamic. 

Internuncial fibers connect the olfactory lobes 
with the centers lower down, namely, with the 
neurones in the spinal cord which innervate the 
muscles on either side of the trunk. In response 
to an impression received primarily through the 



THE PHYSIOLOGY OF MIND 53 

olfactory receptors these muscles contract. The 
neurones which supply the two sides are syn- 
aptically so related that when the muscles of 
one side of the trunk contract, contraction of 
the muscles of the other side is inhibited. The 
result is an alternate contraction of the muscles 
of the two sides, which causes the body of the 
animal to be propelled forward as in swimming. 
The neurone relationships which necessitate the 
alternate contractions and alternate inhibitions 
or relaxations of the two sides are in part direct 
and in part indirect through the cerebellum. 
With these subsidiary problems we ai*e, how- 
ever, not at present concerned. 

Should the chemical impressions be harmful 
or of such a nature as to portend harm, it is 
easy to understand how reverse movements 
should occur and the animal be moved away. 
Everything depends upon the development of 
the internuncial paths. The latter are clearly 
association paths which when once fully de- 
veloped respond accurately and, it is needless 
to add, automatically to the olfactory im- 
pressions. Further, it is very probable that in 
the course of evolution these olfactory impres- 
sions would not necessarily be limited to those 



54 THE PHYSIOLOGY OF MIND 

which merely aflfected the protoplasm of the 
receptors for good or for ill, but for those which 
aflfected the tissues of the organism as a whole. 
While the reader may find objection to the above 
explanation, the fact remains, I think, beyond 
reasonable question that the approach or re- 
treat of the fish in response to olfactory im- 
pressions is a purely automatic phenomenon. 

When we turn our attention to the eye, the 
ear, and the lateral line system of the fish, other 
important and interesting facts suggest them- 
selves. Thus it is exceedingly probable that the 
field of vision is primarily one for the perception 
of moving objects rather than for those which 
are stationary. Food, already perceived by its 
odor, makes also in moving an impression on 
the retina. Owing to the internuncial path- 
ways the action of the olfactory apparatus in 
bringing about contraction of the muscles in 
swimming would now be reinforced. A similar 
eflfect would be exerted if the object also made a 
sound and so excited the ear, or produced coarse 
waves in the water and so excited the lateral 
lines. 

Whatever explanation we adopt, whether we 
consider the olfactory impacts — the chemical 



THE PHYSIOLOGY OF MIND 55 

molecular movements of smell — as establishing 
a line of least resistance, or whether we adopt 
the explanation of these impacts establishing an 
''attraction/' the conclusion is alike inevitable 
that the resulting approach of the fish toward 
the food is, let us repeat, automatic. Similarly 
the reaction of the other ''brains'' to their spe- 
cial receptors — the eye brain, the ear brain, the 
skin brain — must be alike physical and auto- 
matic. 

It may, I think, be safely assumed that the 
other functions of the fish in which the nervous 
system plays a part, such as digestion, respira- 
tion, circulation, and nutrition, are similarly 
automatic; in fine, that all the neural functions 
are automatically performed. The question 
arises can we draw a like conclusion as regards 
the nervous system of the higher vertebrate 
forms, including man? Let us see what the 
facts justify. 

The automatic character of a spinal response 
or reflex must be admitted without question.. 
Secondly, this response is fixed and invariable. 
A similar interpretation must, I think, be ex- 
tended to the responses which involve the brain 
stem, namely, the medulla, the pons, the crura 



V 



56 THE PHYSIOLOGY OF MIND 

cerebri, the thalamus, and the corpus striatum; 
indeed, the brain stem is frequently spoken of 
as a segmental apparatus, just as we apply the 
conception of a segmental apparatus to the 
spinal cord. It is also spoken of as the palaeo- 
encephalon (Edinger) as it represents the prim- 
itive vertebrate brain. To the brain stem we 
must add the cerebellum whose activities are 
alike ''invariable, innate, structurally predeter- 
mined."^ This leaves us as the only structure 
i^permitting a variable response the cerebral 
cortex . • 

It may be here noted that such modifications 
of the invariable response as an animal betrays 
in its behavior under changed external condi- 
tions, such as absence or surplus of food or of 
oxygen, or such changes in response as may have 
their origin in changed physiological states 
within the organism itself, are not here included 
in the expression ^Variable'' response, but rather 
such responses as would suggest, other things 
equal, a volitional act, i. e., ''choice" on the 
part of the animal. "Choice" in this sense is 
manifested by such elementary forms as the 
amoeba, and, as we have seen, by the individual 

^ See Herrick, loc. eit., p. 124. 



THE PHYSIOLOGY OF MIND 57 

cells of the body tissues. How this apparent 
choice is to be explained on purely physical and 
chemical principles we have also seen. Let 
us now take up the 'Variable'' responses of the 
higher vertebrates for detailed consideration. 

The end of the primitive neural tube, the 
telencephalon, also spoken of as the neo-en- 
cephalon, has no segmental relationships. It 
can, therefore, only be in relation with, and 
grow in relation with, the other portions of the 
neural tube. Its neurones in their development 
and multiplication can only establish relation- 
ships with the neurones of the primitive seg- 
mental brain; ingress and egress are possible 
only through the latter. Not having segmental 
relationships, the neurones of the end-brain are 
necessarily limited to the function of intercalary 
neurones. If the end-brain grows in response 
to the stimulus of function — and the facts of 
embryology, comparative anatomy, and pale- 
ontology show that it has so grown — it means 
that a multiplication of intercalary neurones 
has taken place, and as a corrollary an increas- 
ing variability— that is, an increasing "adapta- 
bility" — of response. An increasing adaptabil- 
ity of the responses of the organism to the con- 



58 THE PHYSIOLOGY OF MIND 

stantly changing condition of its existence can 
only become possible through the multiplica- 
tion of intercalary neurones. This multiplica- 
tion permits alike of an increased complexity 
and an increased adjustment of the responses. 
Finally, it is obvious that in speaking of the 
function of tlie end-brain, the cortex, we should 
speak not of the variability of the responses, but 
of the adaptation of the responses. 

In turn, it becomes evident that the responses 
of the end-brain, the telencephalon, have their 
origin in the relation which its neurones bear to 
those of the primitive segmental brain, to the 
neurones of the spinal segments, and to each 
other. Transmission into the end-brain takes 
place through the ''between brain," the thal- 
amus. Here we find that through the develop- 
ment of intercalary neurones, special way sta- 
tions, nuclei, have made their appearance. In 
the cells of the latter various axones bearing 
tactile, visual, auditory, and other impacts ter- 
minate synaptically; thence other axones con- 
stituting the so-called ''sensory projection fibers'' 
pass upward to the cortex. The nuclei in the 
thalamus which play this role of way stations — 
and one of whose functions is doubtless that of 



THE PHYSIOLOGY OF MIND 59 

reinforcement — are spoken of as ''cortical de- 
pendencies"; in vertebrates lacking a corre- 
sponding cortical development they naturally 
have no existence. V 

Responses make their exit from the cortex in 
axones which terminate synaptically not in 
neurones in the corpus striatum but in neurones 
in the brain stem and spinal segments. The 
latter group of axones constitute the motor pro- 
jection fibers and are also spoken of as the upper 
motor pathway or pyramidal tract. Like the 
nuclei of the thalamus, the neurones of the 
corpus striatum doubtless have an action of re- 
inforcement, but it is probable that they do 
much more than this; in lower vertebrates their 
nuclear arrangement appears to be such as to 
permit of relatively complex responses; for ex- 
ample, in birds, in whom the striatum is large 
and the cortex meagre. In higher vertebrates 
they appear to constitute a ready-made mechan- 
ism (neurone combinations) for various auto- 
matic movements controlled or inhibited by the 
cortex; certain it is, also, that the corpus stri- 
atum is in part concerned in the purely dynamic 

^ All of the afferent impulses save those coming from the olfactory 
lobes find their way into the telencephalon through the thalamus. 



60 THE PHYSIOLOGY OF MIND 

function of the maintenance of muscle tone. It 
is clearly evident that in the higher vertebrates 
such responses as have their origin in the stri- 
atum or are transmitted by it are definitely 
fixed; on the other hand, such responses as arise 
in the cortex and are transmitted by the axones 
terminating in the brain stem and spinal seg- 
ments are variable or adaptable- The responses 
so transmitted are adapted to the environmental 
happenings. They are the resultants of, and, 
other things equal, equivalent to, the various 
and multiple impacts received by the organism. 
Having established the avenues of ingress and 
egress and having considered the nature of the 
" responses, the question now arises. What takes 
place in the cortex itself .'^ The sensory projec- 
tion fibers terminate synaptically in certain re- 
gions or areas of the cortex. These areas are 
commonly spoken of as cortical centers for 
smell, taste, vision, hearing, tactile, and other 
impressions. For the present it will suffice to 
regard them purely as gateways or avenues of 
entrance to the general cortex. Similarly, the 
neurones of a certain area— that of the ascend- 
ing frontal convolution in man — give rise to 
axones which constitute the motor projection 



THE PHYSIOLOGY OF MIND 61 

fibers. This leaves extensive regions which 
have no access to the external world either in 
the way of receiving impacts or of transmitting 
them save through such connections, direct or 
indirect, as they may have with the receiving or 
the emissive areas. The facts of anatomical 
structure show that there are extensive and 
numerous pathways- — association tracts — which 
connect different parts of the cortex with each 
other. Some of these fibers form extensive and 
long bundles or fasciculi; others are relatively 
short; others still connect immediately or closely 
adjoining areas of the cortex. In fact, the 
arrangement is such that any one part of the 
cortex is directly or indirectly connected with 
every other part. Finally, extensive commis- 
sural fibers bring about an intimate union of the 
two cerebral hemispheres. T\Tien we reflect that 
the human cortex contains upwards of ten thou- 
,sand million neurones^ and that each neurone 
bears numerous dendrites and that each neu- 
rone sends out one axone, sometimes two, and 
several collaterals, all terminating in numerous 
tuft-like subdivisions, we can realize that the 

^ According to Herrick, loc. cit., p. 27, "some 9280 million," i. e., 
approximately 10,000,000,000. 



62 THE PHYSIOLOGY OF MIND 

number of possible combinations becomes al- 
most infinite. That this leads to great ^S^ari- 
abihty" of the response, or to restate the fact in 
other words, to great possibihties in the adapta- 
tion of the response becomes very evident. A 
given adaptation, as we will see later, is the 
resultant of the impacts received and of the 
previously existing cortical neuronic combina- 
tions. Finally, the conclusion is inevitable that 
the response to the impacts must be automatic. 
Such response is clearly automatic when but 
one neurone is interposed between a receptor 
and an effector, and the factors do not change 
when the interposed neurone becomes multiple. 

A further fact now becomes apparent, namely, 
that as a result of a given impact a very large 
number of neurones may and probably do be- 
come involved in the transmission; the trans- 
mission doubtless takes place not only through 
many hundreds, but through many thousands 
of cortical neurones. In the course of the 
transmission a gateway of exit is finally reached, 
and thence a response is transmitted via the 
brain stem or cord to the effectors. 

Another inference now presents itself, an in- 
ference unavoidable and conclusive, and which 



THE PHYSIOLOGY OF MIND 63 

is of the very greatest importance; and that is, 
if the response is 'Variable/' if it is ''adjust- 
able/' and therefore capable of change, the neu- 
rones of the cortex cannot bear the same fixed 
relations to each other as do the neurones of the 
brain stem and cord. 

Many years ago — in 1895 — in thinking over 
the problems presented by hysteria, it occurred 
to the writer that possibly a hysterical paralysis 
— e. g.^ of an arm — could be accounted for by a 
retraction of the processes of the neurones in 
the ''arm center" of the motor area of the cor- 
tex, so that these neurones would no longer be 
in physiological relation with the rest of the cor- 
tex. In other words, it occurred to the writer 
that possibly the neurones of the cortex had 
some power of movement as far as their ter- 
minal processes, the dendrites, and end-tufts are 
concerned; so that the latter could in some de- 
gree be retracted or extended. An examination 
of the literature revealed that the idea of move- 
ment on the part of the neurone had already 
occurred to three other writers, one in Germany 
and two in France. The first to advance such a 
view was Rabl-Ruckard,^ who in 1890 sug- 

1 Rabl-Ruckard, Xeuro!og. Centralblatt, April, 1890, p. 199. 



64 THE PHYSIOLOGY OF MIND 

gested that nerve-cells have an amoeboid move- 
ment; and he, at the same time, pointed out the 
significance of such a view in enabling us to 
explain the mechanism of psychic processes. 
His ideas attracted no attention, but in 1894 
Lepine/ in a paper on a case of hysteria of a 
peculiar form, advanced practically the same 
theory. His idea was that the neurones were 
capable of movement, and to such an extent as 
to enable them to alter the degree of their rela- 
tion to each other. Some six months after- 
wards another French writer, Mathias Duval,^ 
advanced the same theory in a communication 
made to the Societe de Biologic. Lepine had 
been unaware of the theory advanced by Rabl- 
Ruckard and Mathias Duval, and was equally 
unaware of the views advanced by Lepine. A 
week after Duval had advanced his theory, 
Lepine,^ before the same society, repeated his 
former arguments in its support. I myself pre- 
sented the theory of the movement of the neu- 
rone in a paper read before the College of Phys- 
icians of Philadelphia in January, 1896/ and in 

1 Lepine, Eevue de Medeelne, Aout, 1894, p. 713. 

2 Duval, Comptes Rendus de la Societe de Biologie, Fevrier, 1895, 
pp. 74, 86. 

^ Lepine, Comptes Rendus de la Societe de Biologic, 1895, p. 85. 
^ Trans. College of Physicians, Philadelphia, 1896. 



THE PHYSIOLOGY OF MIND 65 

June of that year read an address on the same 
subject before the American Neurological Asso- 
ciation.^ In the meantime, in the spring of 
1896, the theory had been again advanced by 
two other French physicians, Azoulay and 
Pupin. This view was not accepted by Ramon 
y Cajal.^ He, however, saw the necessity of ad- 
mitting a change in the relations of the neurones 
to each other, and offered the explanation that 
it was the neuroglia cells which moved and not 
the neurones. He maintained that the processes 
of the neuroglia cells represent an insulating and 
non-conducting material, and that during the 
stage of relaxation these processes penetrate 
between the arborizations of the nerve-cells and 
so make difficult or impossible the passage of 
nerve currents; on the other hand, in the stage 
of contraction the processes of the neuroglia 
cells are retracted and they then no longer sepa- 
rate the processes of the nerve-cells, and the 
latter are thus permitted to come into contact. 
Evidently Ramon y Cajal admitted the very 
thing against which he contended, for if the 
nerve-cell processes are at one time not in con- 

^ Trans. Amer. Neur. Assoc, August, 1896. 

2 Ramon y Cajal, Revista de Medicina y, Cirugia Practicas, Mayo, 
5, 1895, p. 497. 
5 



66 THE PHYSIOLOGY OF MIND 

tact and at another are in contact, they cer- 
tainly move. It matters not whether the mo- 
tion is an active or a passive one. Finally, while 
movements of neurones have not been observed 
in vertebrates, one very suggestive observation 
was made in 1890 by Wiedersheim.^ He saw in 
the living animal, an entomostracan, leptodora 
hyalina, the nerve-cells in the oesophageal gan- 
glion move. The oesophageal ganglion may in 
a sense be regarded as the brain of the animal, 
inasmuch as it receives the fibers of the optic 
nerve, and Wiedersheim actually saw these cells 
move and change their shape. He described the 
movement as slow and flowing, and pictures in 
his paper the various shapes assumed by the 
nerve-cells at different times. While it is a far 
cry from the nerve-cells of invertebrate forms to 
those of the vertebrates, the nerve-cells of the 
former, the protoneurones, illustrate, as we have 
seen, elemental truths, and the observation of 
Wiedersheim is in harmony with the view that 
the relations of the primordial neurones are not 
fixed as we find them in the segments of the cord 
and brain stem of vertebrates, but permit of 
change with each other. It would appear that 

^ Wiedersheim, Anatomischer Anzeiger, 1890, p. 693. 



THE PHYSIOLOGY OF MIND 67 

this motility or facility of change lost in the 
cord and brain stem has been preserved in the 
telencephalon. 

Further, we are so in the habit of looking at 
nerve-cells in mounted and stained sections of 
the cord and brain that we are apt to transfer 
the idea of fixation of structure subconsciously 
to our conceptions of the living cells and pro- 
cesses, and to overlook some of the marvelous 
truths which they present. The neurone has 
its origin in a simple undifferentiated cell, the 
neuroblast; in the course of its development it 
sends out processes, some of them of enormous 
length, which in their growth often pass along 
devious routes to a definite destination. For 

instance, certain cells of the motor area of the 

* 

cortex send forth processes, the axones, which 
grow through great distances to come finally 
into relation with neurones in definite segments 
of the spinal cord; and again, other neurones, 
both motor and sensory, send out processes 
which bring the various portions and areas of 
the body into definite relations with them; that 
is, the axones grow out until the;^ reach definite 
effectors or definite end-organs of the body sur- 
face and elsewhere. That this phenomenon 



68 THE PHYSIOLOGY OF MIND 

must be the expression of purely physical or 
chemical causes there can be no doubt. Defi- 
nite causes must be at work, such, for instance, 
as determines the growth of the roots of plants 
toward water. ''Many organs of the adult body 
are known to secrete specific soluble chemical 
substances termed 'hormones/ which diffuse 
throughout the lymph or blood and call forth 
functional activity in remote organs. It is pos- 
sible that during development of the body, the 
organs, as soon as definite stages of growth are 
reached, secrete similar substances which diffuse 
through the surrounding tissue and each of which 
has a chemotactic affinity for a certain type 
of developing neurones. Thus, the developing 
muscles may secrete a substance to which the 
motor neurones of the spinal cord react by a 
growth of their embryonic axones toward the 
source of the stimulating material. ''^ This phe- 
nomenon is known as chemo taxis. The thought 
also suggests itself that possibly this process 
does not cease absolutely with the evolution of 
the organism, but in some measure continues in 
the fully developed organism in accordance with 
changing conditions. 

^ See Herrick, loc. eit., pp. Ill, 112. 



THE PHYSIOLOGY OF MIND 69 

Again, it has been found that in the course of 
the evolution of vertebrate forms nerve-cells 
change their positions. Numerous groups of 
cell bodies with specific functions move from 
their primitive positions to new locations. Our 
knowledge of their migrations is due mainly to 
Kappers. It would seem that cell bodies ''tend 
to migrate in the direction from which they 
habitually receive their stimuli, i. e., in the 
direction taken by their dendrites. If there is 
a change in the direction from which a given 
nucleus (i. e.^ a group of cells) receives its chief 
stimuli, the nucleus as a whole will tend to 
move toward the new source of excitation and 
away from the old.^ The change in position is 
obviously expressive of a physical reaction to a 
stimulus, and the phenomenon has received the 
name of ''neurobio taxis." Both the facts of 
chemotaxis and neurobiotaxis throw an inter- 
esting light on the active, living, growing char- 
acter of the neurone; changing and capable 
of change. Indeed, capacity for change and 
adaptation seems inherent in the primitive 
neuroblast. At times continuous changes and 
fresh adaptations may be the result; at others, 

2 See Herrick, loo. cit., p. 112. 



70 THE PHYSIOLOGY OF MIND 

fixation or relative fixation may be estab- 
lished. 

Let us again turn our attention to the rela- 
tions between the neurones, i. e.^ to the synapses. 
Kappers^ points out that the relations of neu- 
rones to each other vary somewhat. In some 
the relation may be practically one of con- 
tinuity, as when the neurofibrils of one neurone 
pass directly into those of the second; as is often 
the case in the vestibular apparatus. Such an 
arrangement may be expected in the Mauthner 
cell in the catfish — a large cell in relation with 
the vestibular nerve — in which transmission 
probably takes place directly between the ax- 
ones of one cell and the dendrites of another. 
Between other cells the relation may be merely 
that of contiguity or, it may be added, of 
propinquity. At the time of the passage of a 
reflex a delay in transmission occurs at a syn- 
apse. Kappers thinks that differences in delay 
may be due to differences in the synapses. 
Probably this delay is greater when the his- 
tological relation consists merely of contiguity 
and greatest when this contiguity or approxi- 

1 Kappers, Versuch einer Erklarung des Verhaltens an der Synapsis^ 
Psych, en Neurol., Bladen, 1917, H. 6, p. 440; also Brain, July, 1921,. 
p. 125. 



THE PHYSIOLOGY OF MIND 71 

mation must first be established. The last 
would naturally result when a new pathway 
was being formed, or in the case of one that was 
only occasionally used. Kappers regards the 
transmission through the neurone in one direction 
only — i. e., the polarization of the neurone — 
as a neurobio tactic phenomenon. He declares 
that the formation of dendrites and axones is 
the result of the reaction to stimuli; the axone 
is a formed product of the stimuli current; it 
grows with the current, is formed by the cur- 
rent. The dendrite is likewise a formed product 
of the stimuli current. In the passage of the 
current from cell to cell, the axone terminals of 
the first cell are drawn toward the dendrites of 
the second cell, and the dendrites of the second 
cell are drawn toward the axone terminals of 
the first. The mere act of the transmission of 
an impulse brings about an approach, the whole 
process being neurobiotactic. 

Sherrington^ regarded it as improbable that 
the phenomena of the synapse are dependent 
upon an amoeboidism of the neurones, and he 
did so for the following reason: The length of 
the delay caused in a reflex by a synapse — i. e.^ 

^ Sherrington, The Integrative Action of the Nervous System, 1911, p. 24. 



72 THE PHYSIOLOGY OF MIND 

the latent period — is inversely proportional to 
the intensity of the reflex. Sherrington found 
that if the latent period of a reflex produced by 
delivery of the stimulus in its full strength be * 
compared with the latent period of the reflex 
produced in two stages— ^. e., by an ''initial" 
stimulus and an "incremental" stimulus — the 
latent period resulting in the two stimuli reflex 
is longer than in the first, namely, w^hen only 
one maximal stimulus is applied. This result 
he regarded as an argument against an amoeboid 
movement on the part of the neurones; a bridge 
once having been constructed by the initial 
stimulus, there should be no additional loss of 
time. However, Sherrington's results also showed 
that the latent period of the incremental stim- 
ulus is always shorter than that of the initial 
stimulus. As Kappers points out, this fact can 
only be explained by supposing that something 
takes place as a result of the initial stimulus 
which does not take place as a result of the in- 
cremental stimulus; and to Kappers there seems 
no good reason for supposing that the added 
time of the initial latent period is not con- 
sumed by the approach of the colloidal particles 
of the terminal processes. Kappers declares 



THE PHYSIOLOGY OF MIND 73 

that the amoeboidism, and, in any case, the 
neurobiotactic phenomena of nerve-cells, have 
not for a long time been mere hypotheses, but 
are actual facts. 

The interrelations of the neurones have been 
the subject of much speculative thought and 
study. Sherrington who, as just seen, denies the 
amoeboidism of the neurone, expresses himself 
as follows:^ ''At the nexus between cells, if 
there be not actual confluence, there must be a 
surface of separation. At the nexus between 
efferent neurone and the muscle-cell, electrical 
organ, etc., which it innervates, it is generally 
admitted that there is not actual confluence of 
the two cells together, but that a surface sepa- 
rates them; and a surface of separation is phys- 
ically a membrane." 

^Tf the conductive element of the neurone be 
fluid, and if at the nexus between neurone and 
neurone there does not exist actual confluence 
of the conductive part of one cell with the con- 
ductive part of the other — e. g^.,.if there is not 
actual continuity of physical phase between 
them — there must be a surface of separation. 
Even should a membrane visible to the micro- 

^ See Sherrington, loc. cit., pp. 16, 17. 



74 THE PHYSIOLOGY OF MIND 

scope not appear, the mere fact of non-con- 
fluence of the one with the other impKes the 
existence of a surface of separation. Such a 
surface might restrain diffusion, bank up os- 
motic pressure, restrict the movement of ions, 
accumulate electric charges, support a double 
electric layer, alter in shape and surface tension 
with changes in difference of potential, alter in 
difference of potential with changes in surface 
tension or in shape, or intervene as a membrane 
between dilute solutions of electrolytes of dif- 
ferent concentration or colloidal suspensions 
with different sign of charge." 

Regarding this hypothetical membrane Kap- 
pers is of the opinion that by a synaptic mem- 
brane we need not understand an actual mem- 
branous structure, but ''merely an electro- 
endosmotic layer." Again, obviously such a 
membrane if morphologically demonstrable 
would consist of the apposition or fusion of 
two cell walls and, further, the physical prin- 
ciples involved — endosmosis and the possible 
passage of electrically charged ions — would 
apply especially to neurones with fixed synaptic 
relations and perhaps in less degree to neurones 
whose relations were changeable. In any event. 



. THE PHYSIOLOGY OF MIND 75 

it is quite probable that the physical principles 
involved would not differ in essence from those 
that determine the approach of the pseudopod 
of an amoeba to a nitrogenous or other food 
particle. 

Leaving for the time being the consideration 
of this ''electro-endosmotic layer" or synaptic 
^'membrane" and the consideration of the phys- 
ical or chemical principles involved, let us turn 
our attention once more to the reactions of 
the cortical neurone, the neurone of the telen- 
cephalon, to the stimuli, the impacts, trans- 
mitted to it from the segmental brain. In one 
of my earlier papers, read before the American 
Neurological Association in June, 1896, I thus 
expressed myself:^ 

''A sequence of sound vibrations impinging 
upon the peripheral auditory neurones pro- 
duces in them a change, which in turn affects 
the relations which their neuraxones bear to 
the auditory nuclei, and secondarily to the 
auditory cortical neurones. Not only are the 
latter affected by the impressions received from 
the afferent neuraxones, but they, in turn, re- 

^ Dercum, Presidential Address delivered before The American 
Neurological Association (The Functions of the Neurone), The Journal 
of Nervous and Mental Disease, Vol. XXI, No. 8, 1896, p. 522. 



76 THE PHYSIOLOGY OF MIND 

act in such a way as to change their relations 
to each other, and the new positions assumed 
by them will depend largely upon the fact as to 
whether a similar sequence of impressions has 
passed through them before. If so, the old 
combinations will be re-formed. From the 
cortical auditory center there now pass through 
the general cortex a series of combinations 
among the neurones, also along the oldest and 
best-travelled lines, so that a given sequence of 
musical sounds may suggest at first a familiar 
air, a moment later a vivid recollection of an 
opera once heard and seen. In this simple il- 
lustration is embraced the physiology of per- 
ception, of conception, of memory, and the ex- 
planation of the very sequence of thought 
itself." ' 

Setting aside for the time being the dis- 
cussion of the factors of sensation and of con- 
sciousness embraced in the above interpreta- 
tion, let us take up more in detail the various 
other phenomena presented. First, we are im- 
pressed by the fact that time is consumed in 
the transmission of the impact from the moment 
of its reception until it finds motor expression. 
This is known as the reaction time. We have 



THE PHYSIOLOGY OF MIND 77 

already briefly considered the delay which occurs 
at a synapse. It appears to be time consumed 
in the preparation of the synapse for trans- 
mission, ^. e.^ in the ''setting'^ of the synapse 
(to use Sherrington's term), and which con- 
sists possibly in the formation of protoplasmic 
extensions, in the passage of ions, or in the 
establishment of induction. Many studies have 
been made as to the time lost in the passage 
through gray matter of various reflexes, and it 
would appear that the simpler the reflex, the 
shorter the reaction time, and the more complex 
the reflex or response, the longer the reaction 
time; thus a simple spinal reflex in the frog re- 
veals a loss of 0.008 second (Wundt) or 0.014 
and 0.021 second (Buchanan), while the sim- 
plest reaction times measured, in the psycholog- 
ical laboratories vary between 0.1 and 0.2 sec- 
ond,^ and the reaction times as measured by 
physicians between a ''stimulus word" and a 
''reaction word" range from one to two seconds 
and sometimes longer. The time consumed is 
evidently lost in some physical process, as al- 
ready indicated. The transmission of impact 
from neurone to neurone means the overcoming 

^ See Herrick, loc. cit., p. 104. 



78 THE PHYSIOLOGY OF MIND 

of inertia or resistance at the beginning of each 
neurone, i. e., at its dendrite. Each synapse, so 
to speak, presents a new ^ ^neurone threshold'' 
(Sherrington). 

The positions of neurones and their relations 
to each other are, as we have seen, determined 
by the principle of neurobio taxis. According to 
the latter, the dendrites are directed or, rather, 
are drawn toward the sources of stimulation, 
^^ ^., the sources from which the impacts are re- 
ceived; the axones likewise are drawn toward 
the dendrites of the succeeding cell and, in 
given instances, in the course of phylogeny 
even the entire neurone may move. Here we 
are concerned, however, merely with the be- 
havior of the dendrites and axone terminals. 
No doubt the transmission, the diffusion, of an 
impact, to definite neurones, is determined by 
neurobiotactic principles, and in this is to be 
found the explanation of ^'association.'' In 
their early phylogenetic relationships the trans- 
mission of impact from neurone to neurone was 
doubtless determined by propinquity, and in the 
multiplication of intercalary neurones there 
gradually appeared the ' 'common paths" (see 
p. 48). Definite groups of neurones, therefore. 



THE PHYSIOLOGY OF MIND 79 

became associated in the transmission of given 
impacts, e. g.^ of sound, as in the illustration 
quoted above. The transmission did not, how- 
ever, cease in the so-called cortical center for 
hearing in the temporal lobe, but was trans- 
mitted along ''association'' paths to other re- 
gions of the brain. What determines the direc- 
tion of the transmission.'^ Why do the impacts 
break through definite thresholds and thus give 
rise to certain associations.? Doubtless the 
tendency in the primitive nervous system was 
to a general diffusion of impacts, but auto- 
matically, as in the instance of the establish- 
ment in the fish of the common effector paths 
concerned in swimming as a result of the com- 
mon action of the receptors of smell, sight, and 
hearing in determining the approach of the fish 
to food (see p. 54), so impacts entering the 
cortex by way of the organ of hearing would 
probably diffuse more readily toward the cor- 
tical areas for vision than to those of touch, 
smell, or taste; as in the higher vertebrates, 
impacts of sight and sound from a given source 
are very frequently simultaneous. That there 
should be a lowering of thresholds between si- 
multaneously aroused groups of neurones would 



80 THE PHYSIOLOGY OF MIND 

naturally follow. Activity of neighboring groups 
of neurones would necessarily mean an in- 
creased amceboidism. If one group* only *be 
aroused, pathways having once been established, 
there would be a transmission to the others 
which were still quiescent. At any rate, what- 
ever be the explanation, it can, I think, be 
safely assumed that association — i. e.^ trans- 
mission to other neurones- — takes place in ac- 
cordance with physical principles, and, second, 
having once taken place, they take place more 
and more readily with repetition. In other 
words, to use a physiological term, they be- 
come ^'facilitated.'' 

The special trend followed by the cortical 
neurones in their transmission-associations 
doubtless depends upon a number of factors. 
If the experiences are old and often met with, 
the same or similar associations are repeated; 
if they are new experiences, no doubt new com- 
binations are formed, new pathways estab- 
lished. It is probably this quality of neurone 
activity which makes possible additions to our 
knowledge; it becomes thus the basis of all 
training and education. 

However, the function of the neurone of the 



THE PHYSIOLOGY OF MIND 81 

cortex is not merely that of transmission. The 
reception of the impact means not only the 
passage of the latter through dendrites, cell 
body and axone, but also a change in the sub- 
stance of the neurone; a change physical and 
chemical which results in the evolution of 
energy. An active consumption of substance, 
probably the result of an increased oxidation, 
takes place, and a corresponding amount of 
energy is added to the impulse transmitted. It 
is easy to understand that when the latter finally 
reaches the effectors — i, e., finds motor expres- 
sion — it may differ greatly both in amount and 
character from that originally impinging upon 
the receptors. A very small stimulus may 
liberate a large amount of energy. Each neu- 
rone is a storehouse of energy which needs but 
the transmitted tap of the impact to release it. 
Evidently a series of neurones in relation with 
a receptor will intensify the impressions im- 
pinging upon the latter. Such an arrangement 
is especially evident in the olfactory lobe and 
doubtless accounts for the recognition by the 
organism of impacts so excessively minute as 
are those which impinge upon the olfactory re- 
ceptors. Ramon y Cajal has in this connection 

6 



82 THE PHYSIOLOGY OF MIND 

employed the expression ''avalanche conduc- 
tion." Doubtless a similar truth obtains in re- 
gard to the intercalary neurones next in series. 
i. e.^ those concerned primarily in the central 
transmission of the impact, and also and 
finally, in regard to those in relation with the 
effectors. 

That the impact in its course of transmission 
through the various neurones — avalanche con- 
duction or other — undergoes, in addition, con- 
versions in character, is modified, transformed 
into different equivalents is probably equally 
true; but the discussion of this interesting ques- 
tion is deferred for the present. One truth, 
however, remains apparent, and that is that 
the 10,000 million intercalary neurones of the 
cortex add merely to the complexity of the re- 
sponse; the purely physical, automatic char- 
acter of the latter remains unchanged. This 
automatism is as true of the higher vertebrates 
as it is of the lower. The reaction of the fish 
to the environment is clearly automatic (see 
p. 54), and the development of the telencephalon 
merely makes that automatism more complex. 

A discussion which can no longer be deferred 
is that of consciousness. In a consideration of 



THE PHYSIOLOGY OF MIND 83 

nervous phenomena, the problem of conscious- 
ness of necessity obtrudes itself, and, although 
in a study of the simple problems it may be 
ignored, it must finally be squarely faced. 
When we turn our attention to the protozoa and 
more especially to the amoeba, we realize at 
once that a discussion whether such an organ- 
ism is conscious, whether it has sensation, 
feeling, a sense of being, becomes futile. 
We have seen reason to believe (see pages 
12, 14) that the reactions of the amoeba to 
the environment, like that of the white blood- 
corpuscles and the other individual cells of the 
metazoa, are due to purely physical and chem- 
ical causes. If such structures have a sense of 
being, it must be one that is shared by the sub- 
stance and energy of the universe generally; in- 
deed, it must be participated in by that ulti- 
mate expression of substance and energy, the 
electron itself. Are we to infer that ^^senti- 
ency" makes its appearance when the combina- 
tion of a given number of amino-acids results 
in the formation of a substance that is the seat 
of a continuous chemical change featured by a 
simultaneous upbuilding and reduction (see p. 
40), a continuous change that is itself a direct 



84 THE PHYSIOLOGY OF MIND 

result of its reaction to its environment? or, are 
we to defer this conception of sentiency until 
special arrangements for the reception and trans- 
mission of impacts make their appearance? The 
difficulty increases when we approach the more 
complex metazoa. In the contemplation of the 
coelenterates we may be content to set aside the 
question of ''feeling/' but are we justified in 
doing this in the case of insects with their 
obviously complex sense organs and central 
nervous aggregations? Again, are we justified 
in assuming that the cuttlefish in spite of his 
elaborate eye does not ''see/' has not "light 
sensation" of some kind or other? Assuredly it 
is unphilosophical to assume that the fish in 
spite of its enormous olfactory brain does not 
"smell/' or being possessed of eyes and ears, 
that it does not "see/' does not "hear/' True, 
the impacts received by the "nose brain," the 
"eye brain," the "ear brain," and the "skin 
brain" are all transmitted into the common 
paths concerned in swimming, ^^ ^., in bringing 
about automatic approach to or withdrawal 
from objects in the water; yet, though the "eye 
brain" may glow with the sensation of light and 
the "ear brain" ring with the sensation of sound. 



THE PHYSIOLOGY OF MIND 85 

the consciousness of the fish must be something 
very different from that experienced by our- 
selyes. In what does this difference consist? 
Evidently it concerns the function of the telen- 
cephalon. 

Let us for the time being turn our attention 
to the responses to impacts in the higher ver- 
tebrates. In amphibians the situation has 
changed but little from that in fishes; the re- 
sponses are still the invariable, non-adjustable 
responses of a segmental brain. The same may 
be said of reptiles; variable or adjustable re- 
sponses are negligible factors. When we turn 
to birds, the situation has apparently slightly 
changed. In addition to their very remarkable 
and complex automatic ''instinctive" responses, 
there appears to be a capacity, though a:n ex- 
ceedingly limited one, for adjustable responses. 
In birds the pallium — the cortex of the telen- 
cephalon — is still very rudimentary, and if the 
bird does any ''thinking" he must do it with 
his thalamus and striatum. That he does very 
little is quite evident from the behavior of birds 
ordinarily; that he exceptionally does some is 
equally evident from the occasional behavior of 
certain birds, e, g., the parrot. Further, it is 



86 THE PHYSIOLOGY OF MIND 

exceedingly probable^ as we shall see later on, 
that the complex instincts of birds, as well as 
those of mammals, had their origin in adjustable 
responses. 

It would appear that the structures of the 
primitive brain, the palaeo-encephalon, the seg- 
mental brain, as we term it, is of such a char- 
acter as to permit of adjustable responses in 
only a limited degree. However, that such ad- 
justable responses did take place in it originally 
and still do take place in it in birds and per- 
haps in lower forms, though in very small 
measure, is exceedingly probable. In mam- 
mals, however, the function of the segmental 
brain, like that of the spinal cord, is limited to 
non-adjustable responses. Like the spinal cord, 
the segmental brain has been reduced to a fixed 
mechanism. Such capacity for variable or ad- 
justable responses as it may have originally 
possessed has been usurped by the telencephalon. 

Whatever may be the state of consciousness 
in vertebrates other than mammals, it is quite 
certain that in the latter fixed responses play no 
role in consciousness; this is true of the re- 
sponses in the spinal cord, and it is doubtless 
equally true of the responses in the segmental 



THE PHYSIOLOGY OF MIND 87 

brain. Here again the telencephalon has played 
the role of usurper, for the function of con- 
sciousness, as we know it, is limited to the 
telencephalon. 

When we now turn our attention to this 
function of the telencephalon, the following in- 
teresting facts and inferences present them- 
selves. To begin, various acts themselves the 
outward expression — the effector result — of the 
intercalary function of the telencephalon, and 
which when first performed are attended by 
consciousness, may lose this quality when fre- 
quently repeated. Acts the performance of 
which is at first accompanied by a conscious 
effort, may by frequent repetition become largely 
and in some instances wholly * ^automatic," i. 
e., may finally be unattended by consciousness 
either in whole or in part. Many of the acts 
acquired in early life — the use of utensils in 
eating, the adjustments of clothing, the move- 
ments of writing, the movements concerned in 
playing a musical instrument — are all acts 
usually at first performed slowly and with dif- 
ficulty, but later with increasing ease until con- 
sciousness no longer enters into them. The same 
movements frequently repeated necessitate the 



88 THE PHYSIOLOGY OF MIND 

constant repetition of the same association — the 
same combination — among the neurones, and 
sooner or later the movements acquire all the 
character of fixed responses. 

The first inference that is justified is that 
consciousness disappears in proportion as fixa- 
tion is established. Fixation of response means 
the disappearance of consciousness. This in- 
ference leads to another no less interesting, an 
inference that follows as a corroUary, namely, 
that consciousness is present only in the ^^ad- 
justable'' responses; that is, only in those re- 
sponses which are attended by a changing, an 
actively varying relationship among the neu- 
rones. An impact transmitted from the cord 
and segmental brain into the telencephalon 
brings about definite changes in the synaptic 
relations of the neurones to which the impact 
is first transmitted. Thence the impact is 
transmitted to other intercalary neurones, in- 
deed, to many series of the latter in the manner 
already indicated. The transmission of the im- 
pact, subject to reinforcement, may continue 
until motor centers — ^. ^., until neurones in re- 
lation with effector (motor) neurones of the 
segmental brain or cord — are reached, when an 



THE PHYSIOLOGY OF MIND 89 

outward or motor expression results; or the 
transinission may continue to diffuse variously 
through the cortex without a so-called motor 
area being involved. Whatever the course of 
the transmission, it is inevitable that the neu- 
rones concerned are involved in sequence. The 
axone-terminals of the first neurone approach 
and are^ approached by the dendrites of the 
second (see p. 71). The second neurone effects 
a like synaptic approach with the third, the 
third with the fourth, and so on. It follows that 
just as soon as an impact has been transmitted 
by a neurone — i. e., just as soon as it has com- 
pleted its discharge (see p. 81) — its axone ter- 
minals and the dendrites of the receiving cell 
are again retracted, ^. e,, the synaptic relation- 
ship is broken and the neurone is again at rest. 
It is, I believe, a legitimate inference that a 
neurone at rest can have no relation with con- 
sciousness; a neurone at rest, so to speak, is un- 
conscious. It follows, therefore, that con- 
sciousness is only present in the neurones that 
are actively concerned in transmission. Con- 
sciousness is itself a phenomenon of cortical 
transmission. 

Let us at this point consider some of the ele- 



90 THE PHYSIOLOGY OF MIND 

mental facts of consciousness as they reveal 
themselves to our individual experience. What- 
ever consciousness may be, it is something that 
is constantly changing. A sensation, a percep- 
tion, a thought is experienced. A sensation per- 
sists as long as the impacts that give rise to it 
continue; a perception as long as the object 
perceived throws its impacts upon the receptors; 
a thought resolves itself into a train of sequences. 
Each individual instant of time, however, 
whether it is concerned in a momentary sensa- 
tion derived from a single impact or whether the 
sensation be made up of many succeeding in- 
stants of impacts, becomes past history the 
moment it is experienced; it immediately enters 
the past. The same statement applies, of course, 
to a perception, to a thought; in fact, to any 
mental process. While consciousness is con- 
stantly changing from the immediate present to 
the immediate past, it is of necessity also con- 
stantly passing into the immediate future. 
Bergson^ expresses the same facts as follows: 
^Tor consciousness there is no present, if the 
present be a mathematical instant. An in- 

1 Bergson, Mind Energy, transl. by H. Wilson Carr, Henry Holt & 
Co,, New York, 1920, p. 8. 



THE PHYSIOLOGli OF MIND 91 

.J 

stant is the purely theoretical limit which sepa- 
rates the past from the future. It may, in the 
strict sense, be conceived, it is never perceived. 
When we think we have seized hold of it, it is 
already far away. What we actually perceive 
is a certain span of duration composed of two 
parts— our immediate past and our imminent 
future.''^ 

Surely these elemental facts are in accord 
with the principles governing transmission 
through the cortical neurones. This transmis- 
sion is a progressive, continuous thing; receding 
from the point of entrance of the impact and at 
the same time continuously advancing. In con- 
sidering transmission, however, it is important 
to bear in mind that in addition to the mere 
fact of transmission there is the further fact of 
the release of energy (see p. 81), a release in 
which each neurone successively takes part. 
As a result, an impact, thus continuously re- 
inforced, becomes widely diffused. This dif- 
fusion, however, does not take place indiflFer- 
ently in all directions, but in accordance with 
definite principles. To begin with, it is obvious 

^ Thus far only is the writer in accord with Bergson's interpretation 
of consciousness. From this point on Bergson enters a maze of mysticism. 



9^ THE PHYSIOLOGY OF MIND 

that transmission follows the direction of least 
resistance. Evidently the latter will be in the 
course of the most frequently travelled paths, 
those paths in which the amoeboid approach of 
axone terminals and dendrites has been most 
frequently established, or, to phrase it in other 
words, in which ''synaptic resistance" has been 
most frequently overcome. Further, it is prob- 
able that the transmissions, other things equal, 
at first followed the most direct routes to the 
gateways of exit; the demands for adjustment 
of the responses to the environment were in the 
primitive mammalian forms doubtless rela- 
, tively simple; as they are to this day in moles 
and rabbits, insectivora, rodents, and the like. 
However, the organism in response to the in- 
creasing demands made upon it by the environ- 
ment, reacted by increasing its power of adap- 
tation; it underwent, as we say, evolution. 

The telencephalon grew, its neurones became 
more numerous, and its power of adjusting to 
the environment the responses it transmitted 
was correspondingly increased. Numerous ''as- 
sociation tracts," great and small, gradually 
made their appearance, so that every part of 
the cortex became connected with every other 



THE PHYSIOLOGY OF MIND 98 

part (see p. 61). Notwithstanding this increas- 
ing complexity and increased power of adjust- 
ment, notwithstanding the great facihty for in- 
tercommunication, an impact entering the tel- 
encephalon is not diffused universally through- 
out the entire cortex. Doubtless dependent 
upon the nature of the impact — the exciting 
cause — and the special environment in which 
the organism happens to be placed, as well as 
upon other factors already considered (see p. 
79), the transmission pursues a course more or 
less defined. The transmission is not, however, 
entirely limited to this course, for the neurones 
successively involved doubtless discharge their 
energy not only into those in the direct path- 
way of the transmission but also into neighbor- 
ing neurones not directly concerned. There is, 
so to speak, a lateral transmission, but one of 
less dynamic power, and which finally dies out 
within a variable range of the primary activity. 
Consciousness follows the main train, but also 
includes a limited and fading field to either side 
— to all sides, one might say. In a sense, con- 
sciousness is analogous to the visual field with 
its sharply defined central vision and its grad- 
ually fading peripheral areas. The ''field of con- 



94 THE PHYSIOLOGY OF MIND 

sciousness" becomes less and less distinct as the 
main train of activity — ^perception, thought, 
emissive impulse — is departed from. Gradually 
it fades into the subliminal, the subconscious, 
the unconscious. 

Again, the ''train of activity'' is continuous, 
unbroken, during the waking period. Further, 
the inpour of impacts is incessant, and a giyen 
''train'' may be reinforced, deflected, or modi- 
fied in various ways. Cessation of the "train of 
activity" means, of course, cessation of the 
synaptic transmission, a discontinuance of the 
"amoeboid approach" of axone terminals and 
dendrites. Such a discontinuance means un- 
consciousness and, physiologically, sleep. In 
one of my papers,^ read in 1897, I expressed 
myself as follows: "Evidently the neurones 
when functionally active must be in relation 
with each other. Their processes must be either 
in contact or nearly so. Evidently this condi- 
tion is a prerequisite of consciousness. Now 
what happens when the nerve-cells are ex- 
hausted by fatigue, when their volume and their 
cell contents have been diminished, as we have 

^ Dercum, Application of the Theory of the Movement of the Neuron 
Univ. Med. Magazine, April, 1897, See also C. L. Dana, J. A. M. A., 
April 24, 1920, p. 1141. 



THE PHYSIOLOGY OF MIND 95 

every, reason to infer is the case, from the ex- 
periments of Hodge? Evidently their processes 
become retracted and they are no longer in re- 
lation with each other. The neurone isolated 
from the rest by retraction must be without 
function. General retraction of neurones must 
mean absence of function, must mean uncon- 
sciousness, must mean sleep. In other words, 
in sleep the neurones have their processes re- 
tracted; in consciousness their processes are 
extended."^ 

Let us turn our attention to some of the 
other considerations that present themselves. 
Evidently the extent of the field of conscious- 
ness must depend upon the number of neurones 
called into activity, and this, in turn, must de- 
pend upon the impacts received, upon the 
number, intensity, and character of the latter. 
Further, it is the summation of the activities of 
all the neurones aroused at a given time which 
constitutes at that time the conscious indi- 
viduality. The latter must, therefore, be re- 
garded as multiple, as made up of many in- 

^ Lugaro's suggestion that during sleep there is a general diffuse 
extension of all nervous processes instead of a retraction would sub- 
stitute activity for rest, and is, so it would appear, dynamically incon- 
sistent with arrest of function. 



96 THE PHYSIOLOGY OF MIND 

tegers, and of varying from time to time both 
in extent and character. The group activity, 
the united activity of many neurones probably 
gives rise to a community of consciousness, a 
sense of self as something distinct from the 
outside world. A discussion of the degree with 
which man shares this property with other ani- 
mals would be nugatory. Its possession, how- 
ever, by the latter to any extent must depend 
upon the presence of 'Variable/' that is, '^ad- 
justable" responses. Without these a sense of 
self would obviously be impossible. Further, 
this ''community of consciousness" must neces- 
sarily vary in extent from time to time within 
physiological limits; that it varies greatly in 
pathological conditions we will see later on. 

The community of action of the cortical neu- 
rones must inevitably give rise to the function 
X of memory. To make my meaning clear let me 
use the following illustration: A sequence of 
sound vibrations impinges upon the auditory 
receptors and in due course the impacts are 
transmitted to the "auditory center'' in the 
temporal lobe of the cerebrum. Here the neu- 
rones assume relations with each other corre- 
sponding to the impacts received, the character. 



THE PHYSIOLOGY OF MIND 97 

intensity, and other qualities of the latter; the 
impacts are also transmitted to neighboring and 
possibly distant areas. If a similar series of 
impacts has been transmitted by the neurones 
before, similar or the same combinations will be 
re-formed, and as a corollary there will follow 
a recognition by the neurones concerned in the 
communal relation of consciousness as some- 
thing experienced before. That memory is a 
purely dynamic function there can, I think, be 
no question. The capacity for memory must 
depend upon the facility among the neurones 
for re-forming old combinations, and this facility 
must be increased by repetition. In a sense 
memory is the expression of the same tendency 
to fixation of neurone combinations as has 
given rise to the fixed relationships in the palseo- 
encephalon. Perhaps some of the ''instincts" 
and ''race memories" have their basis in com- 
binations of such frequent recurrence in the 
ancestry that they have acquired all the poten- 
tiality of inherited structure. 

One of the most instructive phenomena illus- 
trating the dynamic character of memory is 
that presented bv memorv temporarily de- 
layed. It is a matter of common experience that 



98 THE PHYSIOLOGY OF MIND 

a name which cannot at once be recalled appears 
in consciousness after the lapse of a fraction of 
a second or, indeed, at times after the lapse of 
many seconds, and at a time when the train of 
thought is already occupying another channel. 
It would seem that the impact leading to the 
memory recall had set in motion a group of 
neurones along paths only occasionally used or 
long unused, or along paths subject for the time 
being to synaptic resistance. The significant 
facts are that time is required for the act, and 
that the presentation of the name occurs auto- 
matically. Another significant illustration of 
the dynamic quality of memory is offered by 
the abnormal memory occasionally observed in 
certain defective children, the so-called ''idiot 
savants." The latter may be able to give cita- 
tions at great length of matter which they have 
heard only once and of the meaning of which 
they have no comprehension; not infrequently 
such citations are in foreign languages, of which 
the child is likewise ignorant. Such abnormal 
memories suggest a pathological tendency to 
fixation of the combinations; perhaps a disease 
of the synapses. Further, it is not improbable 
that in these children the tendency to fixation 



THE PHYSIOLOGY OF MIND 99 

of the cortical responses is directly related to 
their idiocy. It would appear that a certain 
plasticity, release, and freedom of combination 
are essential to normal function. 

Referring again to instincts, it is not im- 
probable that some instincts are inherited 
modes of reaction to the environment that had 
their origin in responses which early in the 
phylogeny of the race were adjustable and which, 
owing to constant repetition, became fixed and 
relegated to the subconscious field. However, 
other phenomena apparently instinctive are 
doubtless due to the mere physical reaction of 
the organism to the environment as pointed 
out by Jacques Loeb.^ In these reactions, like- 
wise, the responses being fixed, they play no 
role, or at most only an indirect role in con- 
sciousness. 

In our discussion of the transmission of im- 
pacts through the telencephalon, and especially 
in our discussion of memory, we have already 
laid the foundation for the explanation of vari- 
ous detailed mental phenomena such as per- 
ception, apperception, association, as expressed 

* Jacques Loeb, Forced Movements, Tropisms, and Animal Conduct, 
Lippincott & Co., Philadelphia, 1918. 



100 THE PHYSIOLOGY OF MIND 

in the train of thought, and the transmission of 
the impact through the avenues of exit to the 
effectors. In the act of perception the neurones 
of the cortex which are the recipients of a given 
series of impacts form combinations among 
themselves corresponding to the impacts re- 
ceived. The transmission, of course, does not 
cease here, but continues, as already indicated, 
by association, intracortical and subcortical, 
many neurones being called into activity. The 
combinations successively formed are some of 
them new, others are combinations which are 
the same as or similar to combinations formed 
upon previous occasions. The result is that the 
incoming combinations resulting from the act 
of perception assume relations in part to past 
combinations and in part to combinations 
wholly or partly new. In other words, it is the 
function of the common or community con- 
sciousness of the neurones concerned in this 
activity to collocate the impression received. 
It is this which constitutes the act of appercep- 
tion. The train of thought automatically fol- 
lows. The very act of collocation constitutes 
the train of thought. It is thought, no matter 
how diversified or complex the transmission may 



THE PHYSIOLOGY OF MIND 101 

become. If it finally eventuates in a discharge 
through an emissive gateway, its further prog- 
ress to the effectors is, of course, outside the 
field of consciousness. 

It is evident, let us resume, that the neurones 
of the telencephalon are roused into action by 
the impacts transmitted to them from the seg- 
mental brain. As a result, the neurones in- 
volved in a given transmission extend their 
processes and enter into synaptic relations with 
other neurones, into which they also discharge. 
It is the active neurones alone, as already 
pointed out, which are concerned in conscious- 
ness. Those which are quiescent are those into 
which transmission has not taken place, and 
consequently cannot manifest consciousness. In 
contrast with the field of consciousness, they 
therefore occupy the unconscious field. It is 
further evident that in the progress of a trans- 
mission through the cortex, neurones previously 
quiescent and therefore in the unconscious field 
are brought into action and now become part of 
the conscious field, and at the same time other 
neurones through which transmission has been 
completed again become quiescent and lapse 
into the unconscious field. In other words, the 



102 THE PHYSIOLOGY OF MIND 

conscious and unconscious fields are constantly 
changing; that which at one moment is con- 
scious field at the next moment is unconscious 
field, and vice versa. 

Again, when a transmission passes through a 
group of neurones, the latter react by forming 
combinations among themselves corresponding 
to the impacts received (see p. 76). A repeti- 
tion of the same or similar impacts means the 
re-formation of the same or similar combina- 
tions (see p. 80). This implies the establish- 
ment of pathways of least resistance, and it 
would seem that a single transmission of an 
impact is sufficient to establish such a path- 
way. In other words, the passage of transmis- 
sions establishes ''associations'' among the neu- 
rones. These are manifest only when the neu- 
rones are active, and are merely potential when 
the neurones are quiescent. It would appear 
that when the latter are stimulated by a trans- 
mission, previous combinations are automat- 
ically reproduced. In this lies, I believe, the 
explanation of the physiology of the uncon- 
scious field. ^ The latter is a vast storehouse of 

^I do not like the expression "unconscious mind"; the words are 
self-contradictory. 



THE PHYSIOLOGY OF MIND lOS 

past experiences. These are represented not by 
gross changes of structure, but merely by po- 
tential possibilities. Whether certain combina- 
tions — associations — are re-formed depends en- 
tirely upon whether the neurones concerned are 
reached by a given transmission. 

Further, it is, I believe, a legitimate inference 
that the number of neurones in action at a 
given time is an exceedingly small part of the 
sum total of the neurones of the cortex. It is 
very probable that the number concerned in the 
field of consciousness — in the train of trans- 
mission, in the train of thought — is relatively 
insignificant when compared with the ten thou- 
sand millions of the total. Finally, when we 
consider the number and complexity of both 
the axone terminals and of the dendrites, and 
the fact that every part of the cortex is in rela- 
tion with every other part, we can perhaps form 
a faint conception of the practically limitless 
possibilities of association. Not only may the 
latter consist of combinations representing im- 
pacts the same as or similar to impacts already 
transmitted but also of combinations entirely 
new. The organism is constantly exposed to 
new and changing relations to the environment. 



104 THE PHYSIOLOGY OF MIND 

and to these demands the organism reacts by a 
constant readjustment in its responses. The 
individual from infancy on, from his very ear- 
liest experiences, throughout his training and 
education, up to the complex experiences of 
adult life, is constantly making fresh adjust- 
ments, i. e., new combinations, new associations 
among his neurones. * 

There can be no doubt that the power of the 
continued making of new combinations differs 
in individuals. In the larger number the com- 
binations that are formed resemble those that 
are formed by other individuals under the same 
circumstances, i. ^., who are exposed to the 
same impacts. In others, a relatively small 
number, the combinations differ in a degree 
sometimes slightly, sometimes widely, from 
those formed by the average individual. It is 
the novel character of the associations formed 
among the neurones that constitutes ''origin- 
ality.'' If the novelty of the association be very 
pronounced, it gives rise to ''imagination"; 
originality and imagination are close kin. 

The field of consciousness — i. e., the train of 
transmission^ — is, of course, of relatively greater 
dynamic power than the unconscious field into 



THE PHYSIOLOGY OF MIND 105 

the neurones of which it successively discharges. 
Whether into the field of activity itself fresh 
impacts, impacts derived from other sources 
than that which originallj" gave rise to the 
transmission, find entrance, is purely a question 
of dynamics. If the dynamic level of the active 
field be relatively high, the ingress of disturbing 
impacts is excluded and the original transmis- 
sion pursues its way undisturbed and untram- 
meled. In such case it is open only to impacts 
derived from the same source that gave rise to 
it and which continually reinforce it. It is this 
which constitutes ^'attention." Lack of atten- 
tion, the inability for sustained attention, is due 
to the ingress of interfering transmissions and, 
other things equal, is expressive of a lower dy- 
namic level — i. e., of weakness. 

Similarly, the relatively high dynamic level 
of the conscious field especially when joined 
with novel associations gives rise to ''initiative," 
to the outward expression, to the discharge — 
through the emissive gateways — of the cortical 
energy. Between ''initiative" and "will" or 
"will power" there is again a close kinship. 
Given the exclusion of interfering transmissions 
as in attention, or in that higher degree of at- 



106 THE PHYSIOLOGY OF MIND 

tention to which we apply the term ^^concen- 
tration/' and given a high dynamic level of the 
train of transmission — the field of conscious- 
ness — ^Vill power" is the necessary outcome. 
The dynamic level of the field of consciousness 
— i. e., the output of energy — must inevitably 
depend upon the intensity of the metabolic 
processes, the chemical changes, going on in the 
substance of the neurones and upon the number 
of the neurones taking part. 

To the conception of the purely automatic 
character of the phenomena of transmission, of 
the amoeboid movements and the serial dis- 
charges — ^in short, of the physico-chemical 
changes which constitute the train of conscious- 
ness, we must now add another, or rather re- 
call to our minds a quality of the neurone al- 
ready in part considered. Consciousness im- 
plies ''sentiency" (see p. 84) as a property of 
the neurone. Consciousness without this prop- 
erty would cease to be consciousness. Sensa- 
tion is a self-evident condition of consciousness 
and is inseparable from it. Now we have al- 
ready considered some of the fundamental reac- 
tions of living protoplasm to the incident forces 
of the environment, the gradual evolution of 



THE PHYSIOLOGY OF MIND 107 

special receptors, and the evolution of special 
portions of the primitive brain, the ''segmental 
brain/' into which the impacts are transmitted. 
These are differentiated in the fish into an 
''olfactory brain/' an "eye brain/' an "ear 
brain/' a "skin brain" (see p. 50). The infer- 
ence becomes unavoidable that these structures 
respectively experience the sensations of odor, 
light, sound, and touch (see p. 84). The ques- 
tion now arises what role does the telencephalon, 
the great usurper, play in this respect. From 
the evidence of structure, only one inference is 
possible, namely, that the impacts from the 
various receptors are transmitted to the cortex. 
If transmitted to the cortex they must be still 
farther transmitted, diffused, according to the 
principles indicated in the preceding pages. We 
have no reason to infer that the mode of motion 
of the impact is thereby changed, ^. ^., in pass- 
ing from the neurones of the segmental brain 
to those of the telencephalon or in the passage 
from the gateway of ingress to other areas of 
the cortex; and, if this be true, it can only be 
that sound, for instance, is experienced in every 
neurone reached by the transmission; or light, 
or smell, or touch, as the case may be. When, 



108 THE PHYSIOLOGY OF MIND 

as is frequently the case, transmissions are re- 
ceived simultaneously from several special sense 
receptors, the impacts do not interfere with each 
other. Both the sound and the object that 
produces it may be perceived at the same time; 
one through the receptors, for hearing and the 
other through the receptors for vision. Cor- 
responding neurone associations, as already in- 
dicated, are formed. So it is doubtless when 
the impacts are received from many receptors; 
for instance, of sound, sight, smell, taste, touch, 
all at the same time. This would seem to be a 
necessary result of the elemental reactions of 
protoplasm to the incident forces of the en- 
vironment; a matter which we have already 
fully discussed (see p. 33 et seq.). 

It would appear to be a logical conclusion 
that, in a sense, the entire cortex sees, hears, 
smells, tastes, and feels wherever it is traversed 
by the transmission. The so-called cortical 
centers appear merely to be avenues of ingress 
and egress to the general cortex, as* already 
pointed out. To be sure, the cortex varies in 
its different parts in its detailed structure and 
presents peculiarities in both the receptive and 
emissive areas; e. g., in the ^Visual area" in the 



THE PHYSIOLOGY OF MIND 109 

occipital lobe and in the centers of the ''motor 
area." Here peculiarities of structure are found 
whose function is that apparently of the rein- 
forcement of transmissions. However, the neu- 
rone of the telencephalon appears to have re- 
tained along with its lack of fixation, along with 
its amoeboid movement, the general elemental 
qualities inherent in the primitive neuroblast^ 
elemental qualities which are shared by the en- 
tire cortex. Other things equal, this lack of 
fixation of function, like the absence of fixation 
of the neurone itself, appears to have been and 
still is a necessary condition of its continued 
evolution. Differentiation and specialization, 
therefore, while it has taken place in the cortex^ 
has not interfered with the continued adapta- 
tion and adjustment of responses and the con- 
tinued forming of new associations or combina- 
tions. Sensations are only experienced by the 
neurones taking part in the transmission, and 
these sensations doubtless depend for their kind 
upon the special receptors by which the im- 
pacts are received. The kinds of impact are 
much more nvimerous than would be implied by 
a consideration merelv of the senses of smell, 
taste, vision, hearing, and touch. There are. 



110 THE PHYSIOLOGY OF MIND 

first, the subdivisions of vision; namely, the per- 
ception of moving objects, of form, and color; 
secondly, the addition to the receptors for 
hearing of those for equilibrium and sense of 
position, and, lastly, the addition to touch of 
the senses of pressure, temperature, and pain. 

In addition to the receptors which receive im- 
pacts from sources external to the body, there 
are receptors which receive impacts arising 
within the body. Sherrington, as already stated, 
has termed the first ''exteroceptors" and the 
second ''interoceptors.'' Besides these there is 
a third group of receptors situated in muscles, 
bones, and joints, which give information as to 
the state of these structures when the parts 
concerned are moved. These Sherrington has 
termed "proprioceptors.'' 

It is quite clear, let us repeat, that the specific 
sensations aroused are dependent upon specific 
impacts received. In addition to these, how- 
ever, the neurone when active—^*, e,, when tak- 
ing part in the train of consciousness^ — also ex- 
periences other sensations, namely, those com- 
prised by pleasure, pain, the emotions or af- 
fects. These may be slight, moderate, or in- 
tense in degree. In their production the in- 



THE PHYSIOLOGY OF MIND 111 

ternal secretions, the hormones, and the sym- 
pathetic and autonomic nervous systems play an 
important role; at times the active cause is to be 
sought in toxic substances bred within the body 
or taken in from without. There is every rea- 
son to believe that the impacts which give rise 
to sensations of pleasure and pain affect primar- 
ily neurones in the segmental brain, the palaeo- 
encephalon, namely, ^ ^cortical dependencies" 
in the thalamus (see p. 58). That they are 
transmitted to the telencephalon and that 
they play a role in consciousness and pro- 
foundly influence the train of Jieurone activity 
in the cortex goes without saying. The hor- 
mones or toxins probably act upon the sympa- 
thetic nervous system, upon the neurones of 
the thalamus, and the neurones of the cortex; 
it is probable that in the latter, in many in- 
stances, they act upon the synapses. If this be 
the case, transmission must be profoundly in- 
fluenced. On the one hand, it may be greatly 
retarded or inhibited, as in depressed mental 
states, e. g.^ in melancholia, in which we have 
probably to do with a toxic hormone as the 
cause both of the mental pain and the retarda- 
tion of the mental processes. How much the 



112 THE PHYSIOLOGY OF MIND 

retardation of itself may serve as a cause of 
mental pain is an interesting question; probably 
it also plays a role. Interference with the syn- 
apses doubtless retards the ^^discharge of en- 
ergy" to the neurones next in succession, and 
this "'blocking'' or retardation of function may 
itself be a cause of pain in the neurone. 

In the opposite condition, that of mania, the 
normal resistance offered by the synapses is 
greatly lessened; there is a general release of 
inhibition and it is not improbable that the re- 
sulting increase of discharge, the heightening of 
function, is directly related to the ''expansion,'' 
the pleasurable, aggressive, mental attitude so 
characteristic of this condition. 

Speculation as to the details possible or prob- 
able in the play of the emotions may lead us 
astray, but perhaps a few thoughts as to some 
of the fundamental physical principles which 
may underlie such elementary phenomena as 
pleasure and pain may not be amiss. For ex- 
ample, certain sequences and certain combina- 
tions of sound give us the pleasurable sensa- 
tion which we term "music." The thought 
suggests itself that the impacts transmitted to 
the neurones, ^. ^., the vibrations, are of such a 



THE PHYSIOLOGY OF MIND 113 

character as to be taken up by the molecules of 
the neurones without causing a disruption of 
their structure, or at most, only a minimal con- 
sumption of substance. It is probable that 
sounds which are harsh, discordant, cacapho- 
nous, are painful because they actually cause 
destruction of the neurone molecule. Con- 
sumption of substance accompanies all dis- 
charge of function (see p. 81), but impacts 
that result in motions that are possible to or 
in harmony with the structure of the neurone 
molecule are probably accompanied by pleasur- 
able sensations. Possibly in some such thought 
as this is to be found the explanation of the 
pleasure and pain experienced through the 
other senses. May we perhaps be permitted 
to extend this conception to pleasurable and 
painful emotions.? How markedly the latter 
are at times attended by the evidences of 
physical exhaustion — i. e.^ consumption of sub- 
stance — need hardly be pointed out. The 
relation between general nutrition and a sense 
of well-being is well known. Many factors, 
however, enter into the problem, and a detailed 
consideration of the affective qualities of mind 
would lead us too far afield. SuflSce it to say 

8 



114 THE PHYSIOLOGY OF MIND 

that the elemental qualities of pain and pleasure 
were in primitive forms doubtless related, on 
the one hand, to injurious or destructive influ- 
ences, and, on the other, to the intake of food 
and other physical compliance with the needs 
of the organism. Later, in the course of evolu- 
tion, there ensued specializations and differen- 
tiations of impressions, impressions derived 
both from the external world and from the 
body of the organism itself. At the same time 
special receptors, both extero- and intero- 
ceptors, together with special neurone path- 
ways were evolved. Later, with the increasing 
development of the telencephalon, there came 
a further differentiation in the impressions and 
their corresponding neurone reactions and an 
increase in the adjustment of the response, 
i. e., in the behavior of the individual. Into 
the final result there may have entered, on 
the one hand, physical pain or physical pleasure; 
or on the other, joy, satisfaction, sorrow, dis- 
appointment; or, it may be, a refined feeling of 
altruism or perhaps of an almost impersonal 
regret. 

In the preceding pages the writer has en- 
deavored to apply purely physical conceptions 



THE PHYSIOLOGY OF MIND 115 

to the interpretation of mind. Tlie view that 
mental phenomena are in their essence physical 
finds confirmation in the facts of so-called 
psychophysics. These embrace especially the 
results of the experimental study of the time 
relations of mental processes and of the phe- 
nomena underlying the sense impressions. 
While a consideration of these phenomena 
in detail would here be out of place, let it 
suffice to say that as regards the first, namely, 
the time relations or reactions — the time re- 
quired for the response to sense impressions — 
they are significant in the fact, first, that any time 
at all is required, and secondly, that this time 
is in distinct relation to the complexity of the 
experiment and the condition of the individual; 
^. ^., whether the latter be in good health, 
whether he be fatigued, or perhaps under the 
infiuence of some stimulant or drug, or the 
subject of disease. Clearly, all these factors 
are physical in their nature. In this connec- 
tion the interesting facts of the ^ ^personal 
equation" in the making of astronomical and 
other scientific time observations also present 
themselves. We are forcibly reminded, too, 
of the part which the synapses play in the 



116 THE PHYSIOLOGY OF MIND 

delay of responses; though it goes without 
saying that some time must necessarily also 
be consumed in the transmission through the 
dendrites, bodies, and axones of the neurones. 

It is, however, in the field of the experimental 
studies upon sense impressions that the most 
significant and most convincing results have 
been achieved. It was found, for instance, 
that a sensation aroused by a given impres- 
sion having been noted, an increase in that 
sensation can only be brought about by a 
proportionate increase in the intensity of the 
impression. It was found, further, that in 
order to bring about such an increase of sensa- 
tion, the increase of intensity of the impres- 
sion made upon the receptors must be in a 
geometric ratio to the increase of sensations; 
that is, the intensity of the sensation increases 
in an arithmetic progression, the intensity of 
the stimulus in a geometric proportion. Thus, 
a man capable of distinguishing between the 
weight of 16 ounces and 17 ounces, cannot 
distinguish between 32 a.nd 33 ounces, but 
only between 32 and 34 ounces. Again, a 
man capable of distinguishing between 20 and 
21 grammes, testing a weight of 250 grammes 



THE PHYSIOLOGY OF MIND 117 

cannot tell when an increase is reached until 
12.5 grammes are added. If he looks at a 
light of 10 candle-power he cannot become 
conscious of an increase in the intensity of the 
light until 2 candle-power are added; if he looks 
at a 60 candle-power flame 12 candle-power 
must be added; if it is a 2000 candle-power 
light, 400 candle-power must be added. ^ Similar 
facts obtain as regards the appreciation of 
intensity of sounds and as regards intensities 
of pressure. As regards the senses of taste 
and smell, of temperature, and the various 
somatic and visceral sensations, the conditions 
are such as to preclude very satisfactory experi- 
mentation. However, in regard to the senses 
in which such studies are possible, there can 
be no doubt as to the facts. A physiologist of 
a past generation, Weber of Leipzig, discovered 
these facts more especially in regard to auditory 
a^d cutaneous sensations, and they constitute 
what is today known as Weber's law. Many 
studies have since been made and various 
interpretations advanced, e. g., by Wundt and 
by Fachner, and the facts may be briefly sum- 
marized as follows: an increase of sensation 

^ Ebbinghaus, Abriss der Psychologic, 1909, pp. Q^Q, 67. 



118 THE PHYSIOLOGY OF MIND 

depends, as above stated, upon a proportionate 
increase of the stimulus; the increase of sensa- 
tion is in arithmetic progression, that of the 
stimulus in geometric progression; or, to state 
it in other words, the sensation increases in 
proportion to the logarithm of the stimulus. 

Clearly we have here a hint not as to the 
relations between physical impressions and a 
spiritual world, as various interpretations would 
lead us to believe, but a hint as to the structure 
of the proteins that make up the neurone and 
the physical laws which these proteins must 
obey. In a sense Weber's law is as purely 
physical as the one which tells us that light is 
inversely as the square of the distance and 
must be equally accepted. The facts of Weber's 
law, however, lead — it seems to the writer — - 
to inferences far more fundamental and im- 
portant. We have already seen that the num- 
ber and character of the impacts which living 
protoplasm can take up is comparatively small. 
Only in an extremely limited degree do the 
changes induced in the protoplasm represent 
the changes — the multiplicity of forces — in the 
outside world. To this conception Weber's 
law adds another; namely, that such changes 



THE PHYSIOLOGY OF MIND 119 

as are represented are only approximate; the 
very constitution of the protein molecules for- 
bids an even and continuous recognition of the 
increasing intensity of impacts. If this is true 
of the recognition of so simple a quality as in- 
crease of intensity, may it not be true also of 
other qualities of the impacts? The thought 
that suggests itself is that the changes induced 
in living protoplasm by the impacts are, firsts 
only such as the protoplasm is capable of receiv- 
ing and, secondly, that these may and probably 
do in themselves correspond only imperfectly 
to the changes going on in the outside world. 
We can only be conscious of the changes in the 
protoplasm of our own substance, ^. ^., the 
changes in the proteins of our neurones; our 
knowledge of the outside world is necessarily 
limited to these changes and must of necessity 
be imperfect. Further, our knowledge is purely 
inferential. That multiple qualities of the out- 
side world produce no changes in the proteins 
of the neurones we have already seen; that 
other qualities induce changes which only im- 
perfectly represent those of the outside world 
is, it must be conceded, equally true. ^^Tiat 
are we to say of the memory pictures and of 



120 THE PHYSIOLOGY OF MIND 

the general and abstract conceptions based 
upon these? Of the memory pictures it may 
be said that they can at best represent only 
more or less approximately actual past re- 
sponses to impacts. Of the general concep- 
tions— ^. e.^ the composite pictures resulting 
from accumulated responses — it may be said 
that they are at best imperfect approximations 
to general external truths, and are liable to 
vary and change with additions to the impacts 
and corresponding fresh responses; that is, 
with an increasing experience. When we 
approach the field of abstract conceptions we 
clearly tread upon dubious ground. In reality, 
abstract conceptions represent nothing that 
actually exists in the outside world. At most 
they are artificial pegs upon which to hang 
the logic of our ideas. And, as regards our 
logic, is not this faculty dependent upon our 
own structure, upon the arrangement of our 
neurones, and upon their contained proteins 
and other substances? In how far is it to be 
trusted? Does it not at times lead us into 
gross absurdities? We need but recall the time- 
worn story of the race between the hare and 
the tortoise. Each interval of space existing 



THE PHYSIOLOGY OF MIND 121 

between the two is divisible, and no matter 
how small the space may become it is still 
divisible; indeed, it is inconceivable that the 
space should become so small that it should 
not be still further divisible; and so it becomes 
logically impossible for the hare ever to catch 
the tortoise. Similar vagaries of neurone activity 
doubtless lie at the basis of such abstractions 
as the fourth, fifth, and sixth dimensions of 
space. As regards the fourth dimension, Ein- 
stein, after pointing out the relations of a given 
body to the three dimensions of space, points 
out that all bodies in the universe are in motion, 
and as it takes time for a given body to move 
from one point to another, time is the fourth 
''dimension" of space. To my way of think- 
ing, it would be better to say that time is an 
essential factor in all conceptions of spatial 
relations^; or to put the fact into simpler lan- 
guage, merely to say that ''all space is filled 
with moving matter." Time and the three 
dimensions of space are abstract conceptions, 
but the conception of "dimensions" having 
once been admitted, it becomes logically cap- 

^ In a sense, every measurable element is a dimension, and in this 
sense time is a fourth dimension of space. 



U2 THE PHYSIOLOGY OF MIND 

able of indefinite multiplication; hence the 
fifth, sixth, and further dimensions of space. 
Is there not here an analogy to the logic of the 
race between the hare and the tortoise? In 
one instance there is indefinite division, in the 
other, indefinite multiplication. 

Evidently the logical process must be con- 
stantly curbed, held in check, inhibited by 
the correcting influence of the impressions 
received from the external world. We know 
that the hare does pass the tortoise, and we 
know also, no matter what our mathematical 
friends may say, that the multiplication of the 
'^dimensions" is in crass contradiction with the 
orientation of our senses, ^. ^., with human 
experience. 



A biological interpretation of mind leads, I 
believe, to a more wholesome, a saner concep- 
tion of its functions and limitations. It may 
be noted that in this essay, up to the present 
moment, the word ' 'psyche'' or its equivalents 
and derivatives have not been employed. At 
the very outset the necessity was pointed out 
of laying aside preconceived ideas, prejudices. 



THE PHYSIOLOGY OF MIND 123 

and beliefs. To introduce at this point an 
''immaterial" something, of unknown and un- 
ascertainable character, to insert such a some- 
thing into the problem renders the latter 
hopelessly unintelligible. Further, when we 
pause to consider the intrinsic meaning of the 
word psyche and its equivalents, most sugges- 
tive inferences present themselves. The Greek 
word 4^vx,yi has the primitive meaning of the 
breath: indeed, given the Greek pronunciation, 
the sound is literally that of the escaping 
breath. In primitive times the ''breath" was 
looked upon as the vital principle,' and its 
final escape in the act of dying as the departure 
of that vital principle. The ^v^y^ naturally 
and subconsciously represented the idea of an 
"immaterial" constituent of our beings. A 
similar interpretation is applicable to the Latin 
word spiritus, the primitive meaning of which 
is likewise air, exhalation, breath, and its root 
still forms the integral parts of the words 
respiration, inspiration, expiration. The Latin 
word "mens" is free from such objections, 
for it literally means the mind, the under- 
standing, the intellect, and to me it has 
seemed much more fitting to employ its de- 



IM THE PHYSIOLOGY OF MIND 

rivatives than those derived from ^v^yi or from 
spiritus. 

In conclusion, I may perhaps be permitted 
to say that there is nothing in the position here 
assumed which should shock or give pain to 
any one. The study of the recondite problems 
of human existence is in a sense a study that 
is imperative and should be pushed to its ulti- 
mate conclusions. Our knowledge of the con- 
stitution of the universe as revealed by the 
marvelous truths of radio-activity, of the struc- 
ture of the atom, and by the field opened up 
by Einstein's discoveries and theories, is but 
an expression of this tendency; surely it should 
not be denied us in the study of mind. The 
modern study of the atom reveals it to 
be but an expression of energy, indestruct- 
ible, persistent, unknowable. Does not this 
cause the difference between the old con- 
ceptions of ''materiar' and ''immaterial" to 
disappear.? Does it not make unnecessary — 
as it is impossible — a ''dual'' conception of 
the universe? Finally, we should remember, 
that as regards religious conceptions, each 
human being is entitled to hold such faith as he 
chooses, and, further, that it is the necessary 



THE PHYSIOLOGY OF MIND 125 

and essential attribute of religious faith that it 
should be incapable of scientific proof. A relig- 
ious faith that would be capable of mathemat- 
ical demonstration would be no faith at all. 



ADDENDUM ON THE PATHOLOGICAL 
PHYSIOLOGY OF MIND 

An application of the facts and deductions 
embraced by the within essay to mental disease 
is both obvious and interesting, and the writer 
has thought it fit to add the following para- 
graphs. 

In the body of the essay, the writer has 
pointed out how the retraction of the dendrites 
and axones of the neurones explains the palsies 
and anaesthesias of hysteria. In other words, 
the functional break is referred to the synapses. 
A similar explanation applies to the palsies 
and anaesthesias of hypnosis which, as Gilles 
de la Tourette long ago pointed out, is merely 
hysteria artificially evoked. All of the phe- 
nomena of these states are undeniably mental, 
{. ^., cortical in their origin. This is true alike 
of the motor, sensory, visceral, as well as the 
more strictly mental reactions. In hypnosis, 
for instance, a partial sleep is induced in which 
the admission of impacts from the various 

126 



THE PHYSIOLOGY OF MIND 127 

receptors is inhibited save from those of the 
sense of hearing. The instructions, ^. e.^ the 
suggestions, are made orally by the operator^; 
all other avenues of contact with the outside 
world are for the time being closed. The train 
of neurone activity, therefore, which is set in 
motion by the suggestions of the operator 
pursues its way unchecked, uncorrected, for 
the impressions ordinarily received through 
vision or the other senses cannot gain access 
to the train of neurone activity, the field of 
consciousness. That under such circumstances 
the subject should prove to be exceedingly 
susceptible to the suggestions of the operator 
is not surprising; even when the suggestions 
are in crass contradiction with the situation 
in which the subject happens to be placed 
and with his previous experiences. 

The patient suffering from hysteria while 
not in any sense asleep, as in hypnosis, yet 
resembles the hypnotized subject in being 
abnormally susceptible to suggestion. Both 
Charcot and Gilles de la Tourette long ago 
stressed this factor in their descriptions of 
hysteria. It was Babinski, however, who espe- 

1 Except, of course, in special instances. 



128 THE PHYSIOLOGY OF MIND 

cially pointed out the fact that the symptoms 
have their origin in suggestions that may arise 
from causes within as well as from causes with- 
out the patient. Especially instructive also 
were the facts which Babinski presented in 
regard to the production of special symptoms 
by the medical examination itseK. He pointed 
outj for instance, that the reason hysterical 
hemiansesthesia predominates on the left side 
of the body is because the physician, being 
usually right-handed, has the brush or sesthesi- 
ometer in his right hand, and, facing the patient 
and asking the usual questions, he naturally 
tests the left side of the patient's body first, 
thus suggesting the very anaesthesia he is try- 
ing to discover. Similar facts obtain in regard 
to the induction of other sensory losses and 
other symptoms. The fact, however, of great- 
est importance is that the same or similar 
procedures may be practised upon normal per- 
sons, but without the slightest result. In other 
words, the hysterical subject accepts suggestions 
both direct and indirect; the normal person re- 
pels them. The personality of the hyster- 
ical patient is a very vulnerable one. Hysteria 
is, indeed, a neuropathy of degeneracy. Its 



THE PHYSIOLOGY OF MIND 129 

symptoms are always expressive of a biological 
inferiority, and, in keeping with this fact, it 
presents a large element of heredity. Charcot 
and his pupils regarded hysteria as always 
inherited; all other causes have merely the 
value of provocative agents. It would appear 
that, as in hypnosis, impacts received by other 
receptors than those which serve as the enter- 
ing avenue of the suggestion, fail to reach or 
to adequately enter the train of transmission, 
the field of consciousness. That when the 
field is entered as a result of psychotherapy or 
other cause, or when the suggestion giving rise 
to the symptom ceases to be operative, the 
symptom disappears, is a matter of common 
experience. It Is not my intention here to 
consider the mechanism of hysteria in detail, 
such, for instance, as is illustrated by the 
immediate disappearance of the hysteria of 
litigation when the claim is settled or other- 
wise disposed of, or, of cases in which other 
"mental compensation'' equally powerful oc- 
curs; for this would take us too far from our 
subject. 

The discussion of the phenomena of hypnosis 
and of hysteria leads naturally to the discus- 



130 THE HHYSIOLOGY OP MIND 

sion of dreams; the latter, it should be added 
however, may be entirely normal manifestations 
As in hypnosis and hysteria, there is in a dream 
a field of cortical neurones active during a period 
in which impacts received by the special sense 
and perhaps other receptors are denied access. 
A field of cortical activity, a *^train of trans 
mission'' arising during sleep, may have its 
origin in one of two ways: First, transmis- 
sion of impacts into the telencephalon by way 
of the special sense receptors being suspended 
during sleep, transmission can only arise from 
impacts received from the viscera or from the 
soma generally; i. e., from the interoceptors or 
proprioceptors. Secondly, it is exceedingly 
probable that a train of transmission may be 
started by direct stimulation of the neurones 
by substances circulating in the blood; for 
example, by hormones present in unusual 
amount or modified in character, or by toxins 
resulting from overfatigue or introduced from 
without. The neurones, too, as a result of 
fatigue or other cause, may be abnormally 
irritable. It is exceedingly probable that toxins 
act primarily upon the terminals of the den- 
drites and end-tufts of the axones, i. e,, upon 



THE PHYSIOLOGY OF MIND 181 

the synapses. It can readily be comprehended 
how in this way a train of transmission, a field 
of cortical activity, may arise. The train of 
transmission no matter how arising, being un- 
inhibited, i. e.^ uncorrected, by impacts received 
from the external world, now diffuses along 
pathways of least resistance; former neurone 
combinations are re-formed, many former ones 
are compounded; unusual and bizarre combi- 
nations result. 

Considerations such as the above lead not 
unnaturallv to a consideration of states of 
delirium and confusion. Here we have to deal 
with problems of infection, intoxication, and 
exhaustion; and doubtless with the action of 
toxins and poisons directly and primarily upon 
the synapses and secondarily upon the bodies 
of the neurones. Irregularly occurring, con- 
stantly changing combinations, discharges and 
retractions appear to feature the conditions; 
more active and pronounced in delirium; de- 
layed, slower in confusion; and abolished in 
stupor. In keeping with this interpretation 
we find delirium featured by hallucinations, 
illusions, and unsystematized, fragmentary de- 
lusions. An hallucination is doubtless excited 



1S2 THE PHYSIOLOGY OF MIND 

by the direct action of the toxin on the neurones 
of a special sense receiving area of the cortex; 
quite commonly it involves the auditory or the 
visual area. The disturbance forcing itself 
into the train of neurone activity already 
existing is naturally regarded by the latter, 
the ^^communal consciousness" (see p. 96), as 
something coming from without, and the noises, 
words, or phrases heard or the object seen are 
referred to the outside world. That in delirium 
errors of perception also occur is not surprising. 
An illusion — excluding, of course, errors in the 
receiving apparatus, the special sense organ — - 
is due to a faulty combination of the neurones 
of the cortex in response to the impacts received, 
or to an imperfect or aberrant correlation (in- 
tegration) with combinations previously formed; 
thus occur mistakes in the recognition of objects 
and persons. That the resulting state of the 
communal consciousness should be one of con- 
fusion more or less active according to the 
intensity of the disturbance is what we should 
under the circumstances be led to expect. 

It is one of the essential features of delirious 
and confused states that there is an absence 
of fixation of any of the symptoms. The pic- 



THE PHYSIOLOGY OF MIND 133 

ture is one constantly changing, constantly 
varying; in an active delirium the picture 
changes with kaleidoscopic suddenness; in con- 
fusion much more slowly; while in stupor the 
deadening weight of intoxication and exhaus- 
tion abolish all manifestations whatever. 

In certain mental diseases fixation, on the 
contrary, sooner or later makes its appear- 
ance. In order that its significance may be 
fully appreciated a digression will be necessary. 

There is a group of mental diseases which 
have their beginnings before the foundation 
of the organism is laid. The building material 
is imperfect, poor in quality, vitiated, so that 
the resulting structure crumbles and gives way 
under its own strains. Mental symptoms make 
their appearance relatively early, and this 
caused the early French writers, notably Morel, 
to speak of it as demence precocey a name which 
Arnold Pick long after rendered into the now 
generally accepted term ''dementia prsecox.'^ 
As might be expected, the number of factors 
which enter into the impaired heredity of the 
patients is exceedingly large and varied, e. gr., 
mental and nervous disease, syphilis, alcoholism, 
criminality, prostitution, vagabondage, eccen- 



134 THE PHYSIOLOGY OF MIND 

tricity; in fact, all forms of degeneracy, mis- 
fits, and failures. 

Dementia praecox is essentially an affection 
of endogenous deterioration. It should really 
be spoken of in the plural, as the insanities 
of adolescence, because in keeping with the 
many and varied hereditary factors entering 
into its causation, it manifests itself in many 
forms. Long ago two groups were isolated 
by Kahlbaum, which he termed respectively 
^'hebephrenia" and ''catatonia,'' and to these 
Kraepelin later added a third, "paranoid 
dementia." Later still Kraepelin distinguished 
ten different forms instead of three, but in 
this he has not been generally followed; and 
doubtless largely because, as Kraepelin himself 
admits, there are between the various forms so 
many transitional forms that they cannot be 
sharply delimited. For practical purposes the 
segregation into hebephrenia, catatonia, and 
paranoid dementia is quite commonly accepted. 
Hebephrenia is a relatively simple form, which 
occurs, on the whole, in the younger individuals; 
catatonia is distinguished more especially by 
the addition of certain motor phenomena and 
also presents slight evidences of "systematiza- 



THE PHYSIOLOGY OF MIND 135 

tion'V of the delusive ideas, and occurs, on 
the average, in somewhat older patients. Para- 
noid dementia is distinguished by a more 
pronounced systematization and occurs, on the 
average, in a still older group. That many 
transitional forms are met with need hardly 
be restated.^ 

Space and the objects of this Addendum 
do not permit of a consideration of the symp- 
toms of dementia praecox. Suffice it to say 
that the known facts in our possession point 
clearly to an auto toxic state and exhaustion. ^ 
The onset of symptoms is gradual, usually 
bearing the character of a confusion, some- 
times with varying elements of systematiza- 
tion and, let us repeat, of weakness and ex- 
haustion. That a progressive deterioration and 
a final dementia should ensue seems quite 
natural; and it is this that occurs in the larger 
number of cases. 

^ Because of his interpretation of dementia praecox as a cleavage or 
fissuration of the mental functions, Bleuler invented and proposed the 
name "schizophrenia," which he believes to be preferable to dementia 
praecox. However, cleavages and fissurations of the personality are not 
confined to dementia praecox, but also occur in other forms of mental 
disease as well as in the neuroses. Both the term and the affection lack 
the specificity that would justify its use. 

2 Dercum, The Story of Dementia Praecox, New York Med. Jour., 
Aug. 12, 1916; also Clin. Manual of Mental Dis., p. 108. 



136 THE PHYSIOLOGY OF MIND 

The behavior of the neurones, their synapses, 
and cell bodies, in confusion we have already 
considered. The researches of Fauser and 
others point among other things to the ingress 
into the blood of an abnormal hormone from 
the sex glands. Together with this we have a 
nerve substance inherently defective and feeble 
in resistance. As a natural result there is 
present, in addition to the confusion, a more 
or less marked adynamia of the field of cortical 
activity, the train of transmission. The level, 
the intensity, of the metabolic processes of 
the neurones is lowered. In keeping with this 
there is slowness of speech and poverty of 
thought which eventuate in mutism, in fixed 
positions, stereotypy, automatism, persevera- 
tion, verbigeration; or it may be stupor. The 
train of transmission is reduced to a shallow, 
a narrow, a monotonously trickling stream, 
which may for a time cease altogether. Now 
and anon, tributary currents join what is left 
of the main stream, but they do so irregularly, 
at unusual points, and at variance with the 
orderly sequence of neurone combinations. 
While the cortex is adynamic as a whole, it 
may happen that the field of cortical activity 



THE PHYSIOLOGY OF MIND 137 

is more greatly reduced than other portions. 
Under normal conditions the train of trans- 
mission, as already pointed out, diffuses, dis- 
charges into other and still inactive areas. 
However, if the level of the active field is 
greatly diminished and other portions of the 
cortex become, as a result of the toxic causes 
at work, spontaneously active, and if they 
possess relatively greater dynamic power, the 
direction of the diffusion may be reversed and 
these new activities may flow into the less 
resistant field. It is not necessary to suppose 
that they represent ''complexes" that have 
been ''repressed,'' to use the language of the 
Freudians. They may, of course, represent a 
variety of things;* on the one hand, "wishes" 
and things desired, and, on the other, things 
of which the patient stands in fear and dread; 
but not necessarily either. 

We have already traced the origin of a hal- 
lucination, e. ^., of hearing, and how it breaks 
into the train of transmission and how it is 
naturally regarded by the already existing 
communal consciousness as something coming 
from without. In a similar manner, other groups 
of neurone combinations may, as a result of 



138 THE PHYSIOLOGY OF MIND 

their greater dynamic level, diffuse their energy 
into the less active field. That phenomena of 
cleavages and fissurations of the personality 
should under these circumstances result is 
what might be expected, but this is no reason, 
as has already been pointed out, for giving to 
dementia praecox the specific name of schizo- 
phrenia. 



Let us return now to a consideration of fixa- 
tion which in certain mental diseases sooner 
or later makes its appearance. We have seen 
how in delirium and confusion there occurs 
an ever-changing and ever-varying combina- 
tion among the neurones. Synaptic relations 
are continuously and irregularly made and 
broken. We have seen, also, that in dementia 
prsecox, especially in the younger group, the 
mental picture is that of a confusion, but that 
in the older groups ''systematization'' of the 
delusive ideas may in some degree be present. 
By systematization is meant the arrangement 
of the ideas into logical sequence; in other 
words, a systematized delusion is one which has 
a logical structure. Now, it is the essence of an 



THE PHYSIOLOGY OF MIND 139 

insane delusion that the person holding it is 
incapable of accepting evidence concerning it; 
i. e.^ such evidence as is accepted by ordinary 
men or by normal minds. This can only mean 
that the neurone combinations concerned in 
the delusions are inaccessible. It is entirely 
justifiable to assume that we have here to deal 
with relations between neurones w^hich recur 
with such ease and constancy as to be potentially 
fixed in character. Inaccessibility to conflict- 
ing trains of neurone combinations is a neces- 
sary result. Any impulse approaching the 
neurones concerned merely results in the re- 
formation of the old combinations. In keep- 
ing with this we meet with another fact, and 
that is, that a delusion once fixed becomes 
permanent. This is typically illustrated by the 
history of the various forms of paranoia, and^ 
indeed, in general terms, it may be stated that 
the appearance of systematized delusions in a 
given mental case is always an unfavorable 
omen. 

The application of the physiological prin- 
ciples developed in the within essay to melan- 
cholia and mania has alreadv been indicated 
(see p. 111). In melancholia the retardation 



140 THE PHYSIOLOGY OF MIND 

may properly be ascribed to a depressing action 
upon the function of the synapses of a toxic 
hormone. Possibly to this, as well as to the 
general action of the toxin upon the neurone 
bodies, the mental suffering is to be attributed. 
It would seem a not illogical inference to regard 
the painful delusions so frequently present, 
as secondary outgrowths, as the explanations 
devised by the patient to account for his suffer- 
ings. At all events, the mental distress is the 
essential feature, as witness the cases of simple 
though severe melancholia without delusions. 

In the phase of mania^ as already pointed out, 
the resistance of the synapses is greatly dimin- 
ished; there is a general release of inhibition. 
It would seem that as a result of the toxic 
hormone or other cause at work, the neurones 
evolve and discharge their energy with unusual 
ease and that the latter flows with lessened 
resistance along the cell processes. The patient 
is expansive, aggressive, boisterous, boastful, 
buoyant. He talks incessantly and with great 
rapidity; he rapidly embraces the objects and 
persons in a room in the scope of his percep- 
tions, but fastens his attention upon nothing. 
Illusions of objects and persons, due in part 



THE PHYSIOLOGY OF MIND 141 

to the fragmentary and imperfect character 
of the perceptions and in part to abnormal 
associations, are a natural consequence. The 
associations are usually striking, unexpected; 
often they consist of meaningless rhymes, simi- 
larly sounding words or syllables, puns, mere 
assonances. There is an enormous increase 
in the flow of ideas; but the latter are evanes- 
cent, fugacious, unessential; what we hear is 
richer in words than in ideas. 

The expansion and the enormously increased 
association of mania is in keeping with 
heightened nervous outflow, the increased 
energy discharged by the neurones. Along 
with this are the motor excitement and the 
unusual, the bizarre, the pathological char- 
acter of the associations. We can understand, 
perhaps, why the nervous overflow should 
pass along unaccustomed channels; perhaps, 
also, why the associations lose their intimate, 
elaborate, and finer qualities; why they should 
become coarse or relatively so. Normal acts 
require time, and probably in proportion to the 
amount of detail. In mania the discharges 
appear to be diffused en masse and probabh^ 
along the larger pathways in which the least 



142 THE PHYSIOLOGY OF MIND 

resistance is encountered. Possibly there is 
here an explanation of the coarseness and 
superficiality of the associations. Finally, it 
is probable that fatigue early impairs the 
synapses upon which the finer adjustments 
depend, so that as the case progresses coarse 
and flaring associations alone are present. 

A concluding paragraph upon the mental 
disturbances, the dementias, which ensue upon 
the gross destructive action of poisons, such as 
lead and alcohol, and upon the destruction of 
the neurones by the ravages of the Spirochseta 
pallida and other agents, hardly seems neces- 
sary. The action of these is obvious and the 
details do not here concern us. 



INDEX 



Abstract conceptions, 120 
thinking, 120 

Act of apperception, 100 
of collocation, 100 

Activity, train of, 94 

Adaptation in metazoa of surface 
cell, 23, 42 
of responses, 58, 62 

Addendum on pathological physi- 
ology of mind, 126 

Adequate stimulus, 51 

Adjustor, 47 

Affects, 110 

Alimentary canal, 48 

Altruism, 114 

Amino- acids in proteins, 19 

Amoeba, reaction to environment, 
12 

Amoeboid approach, 94 
movement of dermal membrane 

of sponges, 16 
transmission, 78 

Amoeboidism of cortical neurones, 
63 
of neurone, 71, 73 

Apperception, 99 

Association, 99 
paths, 53 
pathways, 61 

Attention, 105 

Automatic character of spinal re- 
sponses, 55 

Automatism, acquired, disappear- 
ance of consciousness in, 87 



Automatism of memory, 97 
of response in approach to or 

withdrawal from foreign bodies, 

51 
Avalanche conduction, 81, 82 
Axone, 28, 71 
Azoulay, 65 

Babinski, 127, 128 
Bergson, 90 

Biological endogenous deteriora- 
tions, 134 

interpretation of mind, 122 
Blocking, 112 
Brain, ear, 50, 107 

eye, 50, 107 

nose, 50, 107 

skin, 50, 107 

stem, 56 

visceral, 50 
Buchanan, 77 

Catatonia, 134 

Cell, contractile, difiFerentiation of, 
16 

intermediate, differentiation of, 
24 

metabolism, 13 

receiving, differentiation of, iS 

reducing power of, 14 

selecting power of, 13 
Centers, cortical, 60 
Central nervous system, segmental 

relations of, 49 



143 



144 



INDEX 



Cephalic extremity and special 

sense receptors, segmental rela- 
tions of, 50 
Cerebral cortex. 56, 57, See also 

Cortex. 
Charcot, 127» 129 
Chemical impacts, 34 

received by surface cell, 43 

sense, 51 
Chemotaxis, 68 

Coelenterates, pathways for trans- 
mission in, 21 

transmission in nerve net of> 29 
Collaterals, 28 
Collocation, 100 
Common paths of transmission, 48, 

49, 78 
Communal consciousness, 132 
Community of consciousness, 96 
Complexity of proteins, 19 
Composite pictures, 120 
Concentration, 106 
Conceptions, abstract, 120 

of dimensions, 121 
Conduction, avalanche, 81, 82 
Confusion, 131 
Conscious and unconscious fields, 

relative dynamic power of, 104 
Consciousness, 83 

communal, 132 

disappearance of, in acquired 
automatisms, 87 

field of, 93, 95, 101 

in higher vertebrates, 85 

in lower forms of life, 83 

in lower vertebrates, 84 

in responses of adaptation and 
adjustment, 88 

nature of, 90 

relation of phenomena of cortical 
transmission to, 89 



Contact with foreign bodies as 

stimuli, 34 
Contractile cell, differentiation of, 

16 
Contractility of sponges, 16 
Cortex, functions of, 60 
relation of parts of, 61 
responses of, and relations of 

neurones, 62, 63 
transmission through, phe- 
nomena of, 89 
Cortical centers, 60 
dependencies, 59, 111 
neurones, reactions of, 75 

amoeboidism of, 63 
transmission, phenomena of, rela- 
tion to consciousness, 89 



DA.NGERS of abstract thinking, 120 
de la Tourette, 126, 127 
Delirium, 131 
Delusions, 131 
Demence precoce, 133 
Dementia, paranoid, 134 

prsecox, 133, 134 
Dendrites, 27, 71 
Dercum, 36, 63, 64, 65, 75, 94, 

135 
Dermal membrane of sponges, 16 
Diffusion, 20 

Dimensions, conception of, 121 
Disappointment, 114 
Discharge of energy, 112 
Dreams, 130 

origin of, 130 
Duval, 64 
Dynamic levels, 105 

power, relative, of conscious and 
unconscious fields, 104 

quality of memory, 97, 98 



INDEX 



145 



Ear,' 36 

brain, 50, 107 

E dinger, 56 

Effector, 23, 25 

Egress, pathways of, from telen- 
cephalon, 59 

Einstein, 121, 124 

Electro-endosmotic layer, 74 

Element of time, significance of, 
115 

Emotions, 110 

Endogenous deteriorations, biolog- 
ical, 134 

Energy, discbarge of, 112 
release of, 81 

Environment, reaction of organism 
to, 12-19 

Expansion, 112 

Exteroceptive sense, 44, 45 

Exteroceptors, 110 

Eye brain, 50, 107 
spot, 37 

action of, 37 

Fachxer, 117 
Fauser, 136 

Field of consciousness, 93, 95, 101 
physiology of, 102 
unconscious, 101 
Fischer, Emil, 19 

Fixation, appearance and signifi- 
cance of, 138 
Foreign bodies, contact with, as 
stimuli, 34 
impact of, reaction of proto- 
plasm to, 19 
Fourth dimension, 121 
Freudians, 137 

Hallucinations, 131 
Heat, impacts of, 38 
10 



Heat, influence of, on activity of 

protoplasm, 38 
Hebephrenia, 134 
Heredity in hysteria, 129 
Herrick, 39, 45, 50, 5Q, 61, 68, 69,77 
Higher vertebrates, consciousness 

in, 85 
Historical data, 63 
Hodge, 95 
Hormones, 68 
Hypnosis, 126 
Hj^steria, 63, 126 

heredity in, 129 
Hysterical paralysis, theory of, 63 

Idiot savants, 98 
Illusions, 131 
Imagination, 104 
Impacts, chemical, 34 

from movements and coarse 
vibrations in surrounding me- 
dium, 35 

groups of, 52 

of heat, 38 

of light, 37 

physical, special sensations from, 
107 

received by living protoplasm, 34 
Incremental stimulus, 72 
Ingress, pathways of, to telenceph- 
alon, 58 
Initial stimulus, 72 
Initiative, 105 
Instincts, 97 
Intercalary neurones, 31, 48 

effect of, 32 
Intermediate cell, differentiation 

of, 24 
Internuncial fibers, 52 

paths of transmission, 49 
Interoceptive sense, 44 



146 



INDEX 



Interoceptors, 110 

Invertebrates, nervous system of, 

24 
Iris, response to direct physical 

stimulation, 17 

Jelly-fishes, nervous apparatus 
in, 21 
pathways for transmission in, 21 
Joy, 114 

Kahlbaum, 134 
Kappers, 69, 70, 71, 72, 74 
Knee reflex, 32 
Knee-jerk, 32 
Kraepelin, 134 

Lateral line system, 36 
Lepine, 64 

Light, impacts of, 37 
influence on activity of proto- 
plasm, 37 
Limitations of possibilities, only 
such changes as protoplasm 
is capable of receiving, 119 
these changes correspond only 
imperfectly to changes in 
outside world, 119 
Loeb, Jacques, 99 
Lower forms of life, consciousness 
in, 83 
vertebrates, consciousness in, 84 
Lugaro, 95 

Macule acustica, 36 

Mammals, fixed responses and 

consciousness in, 86 
Mania, 112, 139 
Mauthner, 70 
Mechanism of response, 31 
Melancholia, 111, 139 



Memory, 97 

dynamic quality of, 97, 98 

its automatism, 97 

pictures, 119, 120 
Mental pain, 112 
Metabolism of cells, 13 
Metazoa, adaptation of surface 

cell in, 23, 42 
Mind, 11 

biological interpretation of, 122 

interpretation of, physical con- 
ceptions in, 114 

pathological physiology of, ad- 
dendum, 126 

phenomena of, 11 
Morel, 133 
Motor area, 109 

projection fibers, 60 
Movement, response in, 19 
Movements and coarse vibrations 

in surrounding medium, impacts 

from, 35 
Multicellular forms, primitive re- 
sponses of movement in, 15 
reactions of individual cells of, 
13 
Muscle activity independent of 

nervous influence, 17, 18 
Muscle-cell in pore canals of 

sponges, 23 
Music, 112 

Neo-encepiialon, 57 

Nerve net of coelenterates, trans- 
mission in, 29 

Nerve-cells, 27 
change in positions of, in verte- 
brates, 69 
movement of, in invertebrates, 66 
processes of, 27 

Nervous network, structure of, 20 



INDEX 



147 



Nervous system, central, of verte- 
brates, neurone of, 27 
of invertebrates, 24 
of vertebrates, 24 
synaptic, 29 

differentiation of, 27 
of vertebrates, 30 
syncytia, 29 
Neurobiotactic phenomenon, 71 
Neurobiotaxis, 69, 78 

principles that determine, 78 
Neuroblast, 67 
Neuroid transmission, 21 
Neurone, 28 
amoeboidism of, 71, 73 
changes in, 81 
combinations, 59 
development of, 67 
of central nervous system of 

vertebrates, 27 
origin of, 67 
polarization of, 70, 71 
relations, variability of, 133 
threshold, 78 
Neurones, cortical, amoeboidism of, 
63 
intercalary, 31, 48 

effect of, 32 
of cortex, relations of, 62, 63 
relations between, 100 
reforming of old and formation of 
new combinations among, 103 
Nose brain, 50 

Objections to Greek word iw^v 
and its derivatives, 123 
to Latin word spiritus and its 
derivatives, 123 
Olfactory brain, 107 
impressions, 53 
lobes in fish, 51 



Organism, response by, methods of, 

47 
Originality, 104 
Otic vesicle, 36, 38 
Otoliths, 38 

Pain. 110 

mental, 112 

physical principles of, 112 
Palseo-encephalon, 56 

role of, 86 
Pallium, r61e of, 85 
Paralysis, hysterical, theory of, 63 
Paranoid dementia, 134 

states, 134, 135 
Parker, 15, 18, 20, 21, 22, 26, 27, 29 
Pathological physiology of mind, 

addendum, 126 
Pathways, association, 61 

of ingress to and egress from 
telencephalon, 58 

of transmission, definite, estab- 
lishment of, 48, 49 
old and new, 80 
primitive, 21 
Perception, 99 
Personal equation, 115 
Phenomena of mind, 11 
Physical conceptions in interpreta- 
tion of mind, 114 
Pick, Arnold, 133 
Pictm*es, composite, 120 

memory, 119, 120 
Pleasure, 110 

physical principles of, 112 
Polarity of transmission, 30 
Polarization of neurone, 70, 71 
Pore canal, 16 

epithelial lining of, 16 

of sponges, muscle cell in, 23 

membrane, 16 



148 



INDEX 



Precocious dementias, 134 
Primitive pathways of transmis- 
sion, 21 
responses of movement in multi- 
cellular forms, 15 
transmitting apparatus, position 
of, 24 
network, structure of, 26 
Proprioceptors, 110 
Protein, complexity of, 19 
Protoneurone, £4, 26 

function of, 24 
Protoneurones, 66 
Protoplasm, living, capacity of, for 
transmission of motion 
through its own substance, 
19 
changes in structure of, in 
response to changes in out- 
side world, 118 
function of, 37 
impacts received by, 34 
influence of heat on activity 
ot 38 
of light on, 37 
limited capacity of, for recep- 
tion of incident forces of 
environment, 38, 39 
nature of, 40 
reaction to medium, 35 
structure of, 20, 40 
transparency of, 37, 40, 42 
Pseudopod, reaction to environ- 
ment, 12 
Pupin, 65 

RABL-Riickard, 63, 64 
Race memories, 97 
Ramon y Cajal, 65, 81 
Reactions of individual cells of 
multicellular forms, 13, 14 



Reactions of organism to chemical 
impressions of environment, 
34 
to environment, 12-19 
of unicellular forms, 12 
word, 77 
time, 76 
Receiving cell, differentiation of, 23 
Receptor, 23, 25 
Receptors, differentiation of. 42 
limited number of, 39 
physical character of function, 
42 
Reducing power of cells, 14 
Reflex, 31 
knee, 32 
spinal, 32 
Regret, 114 
Release of energy, 81 
Response, automatism of, in ap- 
proach to or withdrawal from 
foreign bodies, 51 
by organism, methods of, 47 
forms of, 47 
in movement, 19 
mechanism of, 31 
Responses, adaptable, 57 
adaptation of, 58, 62 
differentiation of, 33 
exit of, 59 
fixed, 56, 88 
invariable, 56 
of adaptation and adjustment, 

consciousness in, 88 
of cortex and relations of neu- 
rones, 62, 63 
of movement, primitive, in multi- 
cellar forms, 15 
origin of, 58 

possibilities of adaptation and 
adjustment of, 62 



INDEX 



149 



Responses, spinal, automatic char- 
acter of, 55 
variable, 56, 57 

in higher vertebrates, 57 

Roles of other senses, 54 

Satisfaction, 114 
Schizophrenia, 135, 138 
Sea-anemones, nervous apparatus 
in, 21 

pathways for transmission in, 22 
Segmental apparatus, 56 

relations of central nervous 
system, 49 
of cephalic extremity and 

special sense receptors, 50 
of telencephalon, absence of, 57 
Selecting power of cells, 13 
Selective action, 12 
Self, sense of, 96 
Sensation, 106, 109 

of smell, 43 

of taste, 43 
Sensations, special, from physical 

impacts, 107 
Sense cell, 23 

chemical, 51 

of self, 96 

of smell, exteroceptive, 44, 45 

of taste, interoceptive, 44, 45 
Senses of smell and taste, distinc- 
tion between, 44 

roles of, 54 
Sensory projection fibers, 58 
Sentiency, 83, 106 
Sherrington* 44, 48, 71, 72, 73, 77, 

78, 110 
Significance of element of time, 115 
Skin brain, 50, 107 
Sleep, 94, 95. 126 
Smell, sensation of, 43 



Smell, sense of, 44 

Sorrow, 114 

Sound, transmission of, 36 

Sphincter-like action in canals of 

sponges, 16 
Spinal reflexes, 32 

responses, automatic character 
of, 55 
Sponges, 15 

amoeboid movement of dermal 

membrane of, 16 
contractility of, 16 
dermal membrane of, 16 
muscle-cell in pore canals of, 23 
reaction to environment, 16 
sphincter-like action in canals of, 
16 
Stigma, 37 

action of, 37 
Stimuli, 34 
Stimulus, adequate, 51 

word, 77 
Stupor, 131 
Stylatella, 15, 20 

Surface cell, adaptation of, in 
metazoa, 23, 42 
chemical impacts received by, 
43 
Synapse, 27, 28 
Synapses, 70 
Synaptic delay, 71 
membrane, 75 
nervous system, 29 

differentiation of, 27 
of vertebrates, 30 
resistance, 92 
Syncytic nervous system, 29 
Systematization, 138 

Taste, sensation of, 43 
sense of, 44 



150 



INDEX 



Telencephalon, 57 
absence of segmental relations 

of, 57 
pathways of ingress to and egress 

from, 58 
role of, 107 
Thought, 100 
Time, element of, significance of, 

115 
Tourette, 126, 127 
Train of activity, 94s 
Transmission, 20 

common paths of, 48, 49 
in nerve-net of coelenterates, 29 
internuncial paths of, 49 
nem*oid, 21 

of impacts through organism, 47 
pathways of, definite establish- 
ment of, 48 49 
old and new, 80 
polarity of, 30 
primitive pathways of, 21 
principles that govern, 91 
through cortex, phenomena of, 89 
Transmitting apparatus, primitive, 
position of, 24 
in more complex metazoa, 
24 
network, primitive, structure of, 
26 



Transparency of protoplasm, 37, 
40,42 

Unconscious and conscious fields, 
relative dynamic power of, 104 
field, 101 

physiology of, 102 

Unconsciousness, 94, 95 

Unicellular forms, reactions of, 12 

Vertebrates, higher, conscious- 
ness in, 85 

lower, consciousness in, 84 

nervous system of, 24 

synaptic nervous system of, 30 
Visceral brain, 50 
Vision, subdivisions of, 110 
Visual area, 108 

Waldeyer, 28 

Weber, 117, 118 

Weber's law» significance of, 116- 

118 
Wiedersheim, 66 
Will, 105 

power, 105, 106 
Wilson, 16 
Wishes, 137 
Wundt, 77, 117 



